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Raised Flooring Obsolete or Not?
mstansberry writes "In part three of a series on the price of power in the data center, experts debate the merits of raised flooring. It's been around for years, but the original raised floors weren't designed to handle the air flow people are trying to get out them today. Some say it isn't practical to expect air to make several ninety-degree turns and actually get to where it's supposed to go. Is cooling with raised floors the most efficient option?"
...but in lowered walling.
Where else am I going to store my beer so it can stay cold and the boss not find it?
But then where will we keep the bodies?
As long as the space under the floor has a negative or positive atmosphere I can't see how somme turns have anything to do with the air flow.
Says that raised floors may be inefficient if it gets block. Then says alternatives are expensive. Direct AC where you need it, the article says.
Why wouldn't raised floors be bad if you used them properly?
A NYC lawyer blogs. http://www.chuangblog.com/
I thought the raised flooring was just to make the people working there look taller and more impressive, kinda like how they do with pharmacists.
Another big reason for raised floors is to handle wiring. I know companies where it was installed only for this reason. Cooling wasn't even on their minds.
Proverbs 21:19
You say the "experts" debate it, then ask us? Who you calling expert anyway?
Hey! You! get offa my cloud!
Infuriate left and right
Comment removed based on user account deletion
"Look at ME! I use raised flooring in my data center! I get to crawl through it routing cables and playing fort! I'm so special!"
This is all I hear around here. Would you folks please just get a hold of yourselves?
just make the floor grates. Strong enough to stand on, with lots of small holes.
Shheesh,
The Kruger Dunning explains most post on
If we get rid of the raised floors, how am I supposed to impress people with my knowledge of zinc whiskers?
There are two types of people in the world: those who divide people into two types and those who don't.
I interned at ARL inside of Aberdeen Proving Grounds this past summer and when touring the supercomputer room (more like cluster room these days), the guide said they used one of the computers in the room to simulate the airflow in that room so they could align the systems for better cooling. How geeky is that!
The real usefulness is the ability to run cabling from any point A to any point B in the floor space. The cables are all safely hidden beneath the tiles. If you need to access them, just drop your suction cups on the tile and pull it up.
Without the raised floor, you have to put your rats nest of cabling somewhere else, which almost certainly mean vertical. You will still want to run some of those cables horizontally across the room for various reasons, so now you have cables on the floor/ceiling/along wall etc.
Long live the raised floors!
It's in lower power chips, more efficient PSUs, and possibly liquid cooling where the radiator is outside the building (or a heat exchanger to heat pump loop in hot climates).
To paraphrase a popular saying: "It's the COMPUTERS, stupid!"
Inefficient architectures must be discarded to make way for more modern, smaller, COOLER processors.
Let's address the real problem here -- not the SYMPTOM of hot air.
We need to address the COMPUTERS.
If you "get" pointers add me as a friend (116)!
I am waiting for the day where someone invents a computer that doesn't need to be cooled or generate excess heat.
Think about the lightbulb....A standard 60-watt incadescent bulb generate lots of heat. A better design is something like the LED bulbs that generate the same amount of lumens, with much less power, and more importantly little to no heat.
Good design can allow these devices to not generate excess heat, hence eliminating the need for the raised floor.
Just have the whole data center submerged in an inert solution like the one made by 3M (fluorinert?), and have the workers wear scuba equipment.
Most. Efficient. Cooling. Evar!
I thought hot air rises, cold air falls.
The article points out that overhead cooling requires additional fans, etc.
Racks need to be built more like refridgerators. Foamcore/fiberglass insulated with some nice weatherstripping to create a chamber of sorts. Since the system would be near sealed, convection currents from the warm air exaust rising off the servers in the rack would pull cold air down. Cold air goes in through the bottom of the rack, heats up, gets pushed back through the top. This could probably all be done with regular old clothes dryer hosing.
Fans wouldn't even be needed. Most racks aren't designed to be an airtight system though. Every rack cabinet i've ever worked on was holier than the pope. My experience with raised floors made me think they were purely for running tons of cable without making the ceiling look like a spiders nest.
"Regardless of what option works best in your environment, the message remains the same -- for optimal efficiency, direct cooling where it needs to go. "
This is what the conclusion is? Thanks for the technical opinion and detail in explaining what is best. I just wasted two minutes reading this article so you don't have to. Which is probably slightly longer than it took the author to write this garbage.
Someone needs to create an air interconnect standard that lets server room designers snap-on cold air supplies onto a standard "air-port" on the box or blade. The port standard would include several sizes to accomodate different airflow needs and distribution form large supply ports to a rack of small ports on servers. A Lego-like portfolio of snap-together port connections, tees, joints, ducts, plenums, etc. would let an IT HVAC guy quickly distribute cold air from a floor, wall or ceiling air supply to a rack of servers.
Two wrongs don't make a right, but three lefts do.
Laminar flow is more efficient at thermal transfer than turbulent flow.
If the g'vt kept the data on you that google does you'd better believe you'd be calling it "doing evil"
We had an issue where I once worked because we had so many servers the general server room that many different groups used was no longer adequate for our needs, since we were outgrowing our alotted space. Now instead of building us a new server room with the appropriate cooling (which presumably would have included raised flooring) we got a closet in a new building. This is obviously not much fun for the poor people who worked outside the closet, because the servers made a good deal of noise and even with the door closed were quite distracting.
Now, we had to get building systems to maximize the air flow from the AC vent in the room to ensure maximum cooling and the temperature on the thermostat was set to the minimum (about 65 F I believe). One day, while trying to do some routine upgrades to the server, I noticed things not going so well. So I logged off the remote connection and made my way to the server room.
What do I find when I get there? The room temperature is approximately 95 F (the outside room was a normal 72) and the servers are burning up. I check the system logs and guess what, it has been like this four nearly 12 hrs (since sometime in the middle of the night). To make this worse our system administrator was at home for vacation around X-Mas, so of course all sorts of hell was busting loose.
We wound up getting the room down after the people from building systems managed to get us more AC cooling in the room; however, the point is it was never really enough. Even on a good day it was anywhere from 75 F to 80 F in the room and with nearly a full rack and another one to be moved in there is was never going to be enough. This is what happens though when administrations have apathy when it comes to IT and the needs of the computer systems, particularly servers. Maybe we should bolt servers down and stick them in giant wind tunnels or something...
"Some days you just can't get rid of a bomb."
If something is airtight, putting air in one end will move air out the other end.
The problem lies with larger datacenter environments. Imagine a room the size of a football field. Along the walls are rows of air conditioners that blow cold air underneath the raised floor. Put a cabinet in the middle of the room and replace the tiles around it with perforated ones and you get a lot of cooling for that cabinet. Now start adding more rows & rows of cabinets along with perforated tiles in front of each of them. Eventually you get to a point where very little cold air makes it to those servers in the middle of the room because it's flowing up through other vents before it can get there. What's the solution? Removing servers in the middle of hotspots & adding more AC? Adding ducting under the floor to direct more air to those hotspots? Not very cheap & effective approaches...
I know it sounds crazy, but if space is really at a premium, some places might want to consider water cooling their racks. Create one long set of tubing and water blocks that snakes through each blade, use a high GPM water pump, and get that radiator right in front of the AC unit. Or create a water resistant radiator/fan setup and put it outside. It might be hotter outside than inside, but it should still be more efficient than an AC since ACs effectively create heat gradients with the help of electricity. I imagine getting the whole setup outside would make it more efficient, though I don't know enough about thermodynamics to be sure.
We have been using raised flooring in our data center for decades and never had any cooling issues. Granted we have 4 large air handlers for the room but when running a raised floor one must have the proper system in place. Some hardware is designed to get it's air right from the floor and some is not. Our large server racks don't have floor openings so we have vent tiles in the floor on the front side and the servers in turn suck the cool air through. Raised floor is a great place to route cables/power/phones you name it. Just make sure your your air handlers are top notch (audible alarms/water detection/humidity & Temp control).
Not an expert, but I had some HVAC work done recently in my home.
The blower moving the air only has a certain amount of power. Hook it up to a duct ten feet long, and output basically equals input. Hook it up to a duct ten *miles* long -- even a perfectly airtight one -- the power you put into one end will be lost by the other end, because the air molecules lose momentum (and gain heat) as they bounce off each other and the walls of the duct.
Every time a duct turns a right angle, the molecules lose a lot of energy as they largely slam face-on into the duct work. Rounded corners improve the situation, but not perfectly so.
My HVAC designer said that as a rule of thumb, every right-angle turn in a conventional house duct was the equivalent of adding 10 linear feet, in terms of energy lost to heat.
I'm a bloodsucking fiend! Look at my outfit!
The longer the ductwork, the more turns, and the more severe those turns, the more your fans have to work to achieve the same pressure and airflow. This, because of the increased friction in the pipe.
Now admittedly, friction isn't as important to gasses as it is to other states of matter, but it can have an effect, especially in high flow cooling.
For anyone that actually works in a server room this is a very uninformitive article. Also they present the problem, but not any possible solutions.
Our server room is a room in a former library, and we were still able to make raised flooring work (without many hotspots) by selecting the correct tiles to make grates and sealing others off, then have multiple return registers. Our matching room was disigned as a machine room with hot air on one side, cold on the other of each rack, voila, no hotspots. I belive the keys are positive pressure and correct locations for the grating/returns.
More likely the powers that be have overbought capacity, in order to expand the apparent size and importance of their empire. I've seen several computer rooms that could have been replaced with three laptops and a pocket fan.
Heat rises, our original designs back in 2002 for our data center called for overhead cooling using a new gel based radiator system. It would have been a great solution and caused us to go with a lower raised floor, just for cables and bracing. At the time the cost was too extreme to justify the design so we went back to traditional raised floor.
Tile placement on a raised floor is key, only allowing the cool air to be pushed up in the front of your racks and creating hot rows facing your exhaust ends into the same isle. This way the cool air is pushed up from the floor, pulled in through the rack by the server fans, and exhausted, where it can then rise to a vent.
To answer the original question, I think that using raised floors for cooling is not the most efficient solution. Top down chillers that address the heat that is rising off the servers would be better. I just don't know that the price of these solutions has reached a balance for the savings. Even with this design you need something to create a cool pad for your racks to sit on. Many times this can just be the concrete slab of the floor.
True, but IMO not the best way to handle wiring, overhead runs are much easier and cleaner. Every raised floor environment I have worked in was a mess under the floor and a nightmare to run new cables through.
If cooling is not a concern, concrete slab with overhead runs is the best way. If cooling is an issue, use raised floor, for cooling only and overhead runs for cables.
I used to work in a large building which had air ducts for heating/cooling. Unfortunately, the air pressure wasn't well balanced to compensate for the location of the Sun and office walls (which were added after the office block was built). So people ended up with either freezing cold blasts of air (the North/West sides), or being cooked by the heat of the Sun ( South/East sides). Those in the centre got no natural daylight at all and in those offices at the end of the air duct the air would become stale if the doors were closed.
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
Where I've worked it was primarily for running wires, not cooling. I've also worked in places that have the overhead baskets, and quite frankly, although they are convenient, they are 'tugly. They are great for temporary installations and where stuff gets moved alot, but I'd rather have my critical wires away from places where they can get fiddled with by bored individuals.
So, no, I don't think they will be obselete any time soon. But hey, I'm an old punchcard guy.
"Some say it isn't practical to expect air to make several ninety-degree turns and actually get to where it's supposed to go."
I wonder how all those ducts throughtout America (with tons of 90 degree turns) carry air that heats and cools houses and office buildings every day?
I'm in a data center right now with two rack mounted clusters and three IBM Z series machines plus a load of other kit. Without the raised flooring AND the ventilation systems things would get pretty toasty here but it has to be done right. The clusters are mounted in back to back Compaq network racks which draw air in the front and push it out the back. We therefore have 'cold' isles where the air is fed in through the raised floor and 'hot' isles where the hot air is taken away to help heat the rest of the building.
The only other option would be water cooling but that's viewed by my bosses as supercomputer territory.
Ed Almos
The more corrupt the state, the more numerous the laws. - Tacitus, 56-120 A.D.
They added the Sun after the office block was built? Now that's one old office block!
USE HOT GRITS WITH STATUE OF NATALIE PORTMAN (NAKED AND PETRIFIED)
Very difficult to track down random machine failures to bad interior decoration choices!
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
Put a cabinet in the middle of the room and replace the tiles around it with perforated ones and you get a lot of cooling for that cabinet.
Maybe this is the problem. Every industrial datacenter I have been in places racks over either empty spaces, or tiles with a large vent in them. The rack has fans in it to force air through vertically (bottom to top). A few perforated tiles get scattered about for the humans, but I have been in some datacenters without them to maximize airflow to the racks. But then again, I have worked with electronics that make current CPUs feel like popsicles in comparison.
(S(SKK)(SKK))(S(SKK)(SKK))
At my office we hide all of our broken hardware under the floor so the boss doesent find it and ask questions.
it can turn on a dime, but also stay on that dime. poor circulation results. trumpets have nice (if tight) curves, and even building ducts can have redirects inside the otherwise rectangular ducts to minimize trapped airflow in corners. for the most part even those corners are curved to help the stream of air.
most server rooms aren't part of the duct, for example, the one here is large and rectangular, with enormous vents at either end. not very well designed.
airflow is a very complicated problem, my old employer had at least three AC engineers on full time staff to work out how to keep the tents cold ( I worked for a circus, hence the nick.) the ducting we had to do in many cases was ridiculous.
why do you think the apple engineering used to use a cray to work out the air passage through the old macs. just dropping air-conditioning into a hot room isn't going to do jack if the airflow isn't properly designed and tuned. air, like many things, doesn't like to turn 90 degrees, it needs to be steered.
-- it's ridiculous how many people misspell ridiculous... (damn, damn, damn...)
We worked very closely with Liebert ( http://www.liebert.com/ ) when we recently rennovated our data center for a major project. The traditional CRAC (Computer Room AC) units supplying air through a raised floor is no longer viable for the modern data center. CRAC units are now used as supplemental cooling, and primarily for humidity control. When you have 1024 1U, dual processor servers producing 320 kW of heat in 1000 sq ft of space, an 18 inch raised floor (with all kinds of crap under it) is not adequate to supply the volume of air needed to cool that much heat in so small a space.
We had intended to use the raised floor to supply air, but Liebert's design analysis gave us a clear indication of why that wasn't going to work. We needed to generate air velocities in excess of 35 MPH under the floor. There were hotspots in the room where negative pressure was created and the air was actually being sucked into the floor rather than being blown out from it. So, we happened to get lucky as Liebert was literally just rolling off the production line their Extreme Density cooling system. The system uses rack mounted heat exchangers (air to refrigerant), each of which can dissipate 8 - 10 kW of heat, and can be tied to a building's chilled water system, or a compressor that can be mounted outside the building.
This system is extremely efficient as it puts the cooling at the rack, where it is needed most. It's far more efficient than the floor based system, although we still use the floor units to manage the humidity levels in the room. The Liebert system has been a work horse. Our racks are producing between 8 - 9 kW under load and we consistently have temperatures between 80 - 95 F in the hot aisle, and a nice 68 - 70 F in the cold aisles. No major failures in two years (two software related things early on; one bad valve in a rack mounted unit).
But it also eliminates the joy of making fun of coworkers who gets lost in a raised floor, or closing them in when they go on a hunt for something...
(S(SKK)(SKK))(S(SKK)(SKK))
If you have a water based cooling system (chillers) and you spring a leak... a nice raised floor with deep side channels will save equipment while you figure out how to shut off the water.
I worked for a circus, hence the nick
I thought I smelled cabbage.
Standard racks tend completely to ignore this. They rely on the internal modules handling their own airflow with fans, which is fine if the inlet area to the modules is much less than the size of the duct entering the cabinet. But if the total area of the inlets to the modules is more than the incoming duct area, the modules furthest from the duct (i.e. the ones at the top) will be starved of air. 1U servers are inevitably going to worsen the problem because they create a large number of competing inlets, stratified up the cabinet. Sucking air out at the top will only work if the air flow is so great it creates a significant pressure drop across the servers, which leads to noise problems, is inefficient, and may adversely affect local cooling inside the server. Blades are potentially much better because, with fewer modules in the cabinet, each with similar requirements, it should be easier to design a cabinet-wide ducting system. However, the most logical solution is to go back to designing the entire cabinet as an integrated system - in which case the entire base of the cabinet can be the inlet duct opening, with appropriate internal structures and blade design to fulfil the objectives of keeping consistent flow to each blade rack and across each blade.
It's the old engineering issue - ad hoc design leads to suboptimal results, and systems need to be considered as a whole. Blades are, depending on how you look at it, a step in the right direction or a return to the way things used to be designed when real computers were loads of tight packed boards full of ECL and proper cooling design of the cabinet was essential if the thing was to work at all.
Pining for the fjords
I have been in high density server rooms where the number of tons of AC was no more than 10% higher than the amount of heat produced and the rooms could be made to work with careful placement of vents.
Things can be made better by using overhead returns.
If you start putting the AC units in the racks you need to pipe chilled water to them (which probably needs a raised floor for the pipes) and you will also lose a large amount of rack space from the AC unit.
A rack of 40 1u servers will produce 12.8 kw of heat and require around 4 tons of AC to take care of, if you use cold row/hot row and put the vents in the cold rows, and the overhead return intakes over the hot rows it can generally be done without too much trouble. The only other option is to put small chilled water units in each rack and putting less machines per rack, and having lots of piping in the room this would have the problem of also making new rack installs quite a process.
Turning air 90 degrees is not silly at all. Anyone in HVAC knows that you lose 25% of your force (air-force?) with every 90 degree turn. Designing an HVAC for a house is a series of trade-offs -- you need to work around the available wall space and the desire to get the most out efficiency of your furnace or air conditioner.
Per Square Mile, a blog about density
Oxygenate the fluid, and you can even dispense with the scuba gear...
Going to have to bugdet for towels, though...
One the facilities (gov't) that I have meetings at, has a raised floor covering the entire building. Yes, it is one story and you can place a few football fields in it. They have the ventilation in the overheads and the cabling run under the floor. It works nicely for them, and provides a clean appearance for the entire facility.
http://ask.slashdot.org/article.pl?sid=05/02/23/19 56217&tid=164&tid=4
An Ask Slashdot question was posted back in February about the merits of raising a floor on a budget. Not a dupe, but a complimentary article.
can be read here ...
Hulk SMASH Celiac Disease
With a properly designed raised floor setup in a data center, it makes everything so much easier, easier to run cable, easier to identify power, easier to vent air where it needs to go. I never heard of raised flooring being outdated. What are the alternatives to raised floors? Ladders between sets of racks? What a mess. . .
YOU'RE WINNER !
Another lame blog
A raised floor with holes under the system racks is one way to get the coolest air where it is needed most. But, thermodynamically speaking, it all comes down to how many joules of heat need to be exchanged. If enough heat flows to a cooler area to keep the operating temperature of the systems within recommended specifications, then it does not really matter if it is done through a raised floor.
In terms of efficiency, a raised floor may not be as good as direct ducting and feeding past the hottest components in the systems. But it may be the most reasonable and cost effective way to set up an environment.
Personally, I find that an environment that is good for computers is uncomfortable for humans. Blowing fans and cool air seem to contribute to every cold I get. Coincidence? Probably not since the fans are very good at distributing particulate matter. When liquid cooling comes along, or computers can run at low voltage and amperage, we will be better off.
Have you Meta Moderated t
The more important factor to maximize the efficiency of your cooling system is to get the heat out and back to the AC before it can mix with the cold air feeding your gear.
As long as you set up the datacenter with hot aisles (the backs of the rows face each other pushing the hot air into that aisle), and have return air grills directly above this aisle to take the heat back to the AC, you should be able to feed the cool air to the 'cold' aisle from either below or above. Many older data centers that push cold air into the floor just have an AC unit with an open top (no ducting) sucking in 'warm' air from the 'upper part' of the room, but it may be 30-40 feet to the other end of the space, and that's a lot of room for mixing as the hot air makes it's way down to the unit.
We just completed a small datacanter remodel with supply and returns in the ceiling (our pre-exisiting raised floor is only 6" high and has too many wires for adequate airflow) and it works great. I have 17 racks requiring 12 tons of cooling in a room that is only 25'x25', and they key to the whole thing is the return air grills sucking the hot air out right where it is being expelled by the gear!
I wonder which solution is easiest on the people who have to maintain wiring and ducting.
With raised floors you're working DOWN while running your cabling up under a drop ceiling (or not) has people standing on ladders. Even with bad knees I'd rather work closer to the floor if I have to go fishing in the infinite cable harnesses.
Yes air can turn on a dime.
But the harder you make it turn the bigger the pressure drop and it lowers your overall fluid flow.
90 deg turns are horrible.
The effects of airflow and pressure change can be very significant. Think of an aircraft in flight for example.
That would make maintenance fun: "Oh oh! Got a blade down! Get the scuba gear! YAAAAHOO!"
[You have a stable society when some nut guns down a schoolyard and the law doesn't change.]
Then all you'll need is a lounge chair and a habachi grill and you've got yourself one kick ass pool party.
Wiring is now usually ABOVE the equipment, and with 10Gigabit copper, you can't just put all of the cables in a bundle any more, you have to be very careful.
It's a brave new datacenter world. You need some serious engineering these days, guessing just isn't going to do it. Hire the pros, and save your career.
--Mike--
So long as you have positive air pressure under your floor, you'll get *some* effect from your perf tiles. However, as I'm sure some fluid dynamics folks will jump in with, air flow is a HARD problem. Yeah, so you're getting cold air coming up through your perfs. Well, most of them. Some of them are actually pulling air DOWN. Why?
:)
If you're bored, check out TileFlow. It's an underfloor airflow simulator. You put in your AC units, perf tiles, floor height, baffles, you name it. It will (roughly) work out how many CFM of cold air you're going to see on a given tile. It's near-realtime (takes a second to recalculate when you make changes), so you can quickly add/remove things and see the effect. I spent some time messing with this a couple of years ago, and it's very easy to set up a situation where you have areas in your underfloow with *negative* pressure.
The article basically summed it up for me:
McFarlane said raised floors should be at least 18 inches high, and preferably 24 to 30 inches, to hold the necessary cable bundles without impeding the high volumes of air flow. But he also said those levels aren't realistic for buildings that weren't designed with that extra height.
I'd go with 24 inches MINIMUM, myself. Also, proper cable placement (ie: not just willy-nilly) goes a long way towards helping airflow issues. Like they said though, you don't always have the space.
Of course, with the introduction of a blade chassis or 4, you suddenly need one HELL of a lot more AC
Endless arguments over trivial contradictions in books written by ignorant savages to explain thunder in the dark.
I thought it was one of the funnier things I've read all day. I honestly don't understand why it is modded down as Troll. He doesn't claim first post or make any derogatory comments. Is the first post automatically assumed to be a Troll and modded accordingly? That doesn't quite make sense; then again Slashdot "editors" don't actually edit, so I guess it doesn't really matter.
Good job to the parent; shame to the system.
Then again, a lot of these rooms I've seen have wide open plenum areas as well. These companies get all this expensive security enhancements with combination/card entries, video survelence, digital sign in logs and the ceilings are wide open. Getting back to the subject these wide open celing areas just let in more hot air.
I hope you dont live near me, locusts and other plauge would realy put a damper on my property value.
Having worked in several sites with both raised flooring and without, I would prefer raised flooring for the server room every time. For both wire management and for cooling.
The best use is to have your power distribution run below the floor, to have specific tiles with cut outs to allow cool air to enter the bottom of the racks, and to prevent unexpected disasters like burst water pipes from flooding the room.
There are A/C units available for server rooms are designed to send cold air out from the bottom into the crawl space, and they should be spec'd to supply far more cooling than is require. And there should be at least one primary and a backup unit too.
At one site, we had both A/C units fail one night. The temperature inside one of the cabinets containing some of our network switches reach 155' F, according to the temp sensors inside the switches. Fortunately, we only lost one old server that was on the top shelf of one rack. The temperature in the room reached about 140'F (40'x80' or so) within only 3-4 hours. The room housed about 25 servers, a phone switch and a UPS. The only thing that saved the rack mounted servers was the chimney effect of having the air flowing up throught the racks.
For companies who don't see the value in using something like raised flooring, they have never had to face the prospect of replacing all of their servers if their underpowered A/C supplies fail. For the extra few thousand dollars it costs, it's a worthwhile ounce of prevention. To put things in perspective, the most valuable server in the site I was working in cost almost $250,000. Hate to be the Facilities or IT Manager who had to report the lost of an asset like that.
Link to interesting .pdf regarding zinc filamentation in datacenters. Another fun issue for raised floors and/or old datacenters.
The article seems to question raised floor cooling, and state that it is rarely done right at the same time. To paraphrase: 'Raised floors should be 18", and preferably 24 - 30" to accomidate all the crap that goes down there. But that is not possible in buildings not designed for the raised floor.'
Raised floor cooling is built around a couple of assumptions: 1)The amount of cold air pumped into the floor will be adiquate for the heat above it, as well as the vent area to be serviced. 2) There will be a way to pump the hot air out of the ceiling. 3) The room will be relatively sealed.
With a sealed room, Hot air being pulled out of the top, and cold pumped into the correct places below - and a sealed room: Hot air out, cold air in. It is true that the vents near the fan are higher pressure than the ones further away. This just means that since more air will go through, you need fewer of them for equilivant cooling. The key is adiquate AC for the heat, and pumping the heat out to lower the load on the AC (Think 2' or larger exaust fan.).
As the article points out, you need space for laminer flow of the air past all the crud (Network & Power cables, beer, blow up doll,stun gun, etc..)under the floor. This means that the height of the floor should be near the height of an AC stack (think home low flow AC ~18") after removing 6" of that height from the calculation (think big bundle of wires...).
In terms of Moores Law, everything but a Hosting site should not need an air floor since it can now be handled by fewer computers. I remember going to Trump Casino's Data Center. Big room (Think Football Field): Raised Floor. They had very few machines and the place was cold as heck -> Why? Because they had replaced all their giant mainframes with new IBM midrange stuff. More processing power & Less heat. Of course they had to replace a crapload of vented flooring, but I digress.
The Problem with raised flooring is that it is not done correctly (not enough height), or the AC is not upgraded when the heat requirements demand it (too many computers for the thermal load rating of the AC). This is because a) Managment wants raised floor cooling in buildings without the headroom for it, and b) because they want more servers and will be dammed if they think about ancilliaries like AC, they allready did not budget for those damn UPS and Tape backup units...
my hometown got a datacenter a few years ago, and it's all overhead cabling. of course, it's also a converted departement store, so that's natural.
When you are designing for a space (such as a room) you design for the shortest amount of ductwork for the greatest amount of distribution. Look up in the ceiling of an office complex sometime and count the number of supply and return diffusers that work to keep your air in reasonable shape. All of the ducts that supply this air are smooth, straight and designed for a minimal amount of losses.
All air flow is predicated on two imporant points within a given pipe (splits and branching with in the duct work is not covered here): pressure loss within the pipe and how much power you have to move the air. The higher the pressure losses, the more power you need to move the same amount of air. Every corner, turn, rough pipe, longer pipe all contribute to the amount of power needed to push the air through at the rate you need.
Where am I going with all of this? Well under floor/raised floor systems do not have alot of space under them and it is assumed that the entire space under it is flexible and can be used (ie no impediments or blockages). Ductwork is immobile and does not appreciate being banged around. Most big servers need immense amounts of cooling. A 10"x10" duct is good for roughly 200 CFM of air. That much air is good for 2-3 people (this is rough, since I do not have my HVAC cookbook in front of me.. yes that is what it is called). Servers need large volumes of air and if that ductwork is put under the floor, pray you don't need any cables in that area of the room. Before you ask: Well why don't we just pump the air into the space under the floor and it will get there? Air is like water, it leaves through the easiest method possible. Place a glass on the table and pour water on the table and see if any of the water ends up in the glass. Good chance it ends up spread out on the floor where it was easiest to leak out. Unless air is specifically ducted to exatcly where you want it, it will go anywhere it can (always to the easiest exit).
Ductwork is a very space consuming item. Main trunks for 2 and three story buildings can be on the order of four to five feet wide and three to four feet high. A server room by itself can require the same amount of cooling as the rest of the floor it is on. (ignoring wet bulb/dry bulb issues, humidity generation and filtering, we are just talking about number of BTUs generated). A good size server room could easily require a seperate trunk line and return to prevent the spreading of heated air throughout the building (some places do actually duct the warm air into the rest of the building during the winter). Allowing this air to return into the common plenum return will place an additional load on the rest of the buildings AC system. Place the server on a seperate HVAC system to prevent overloading the rest of the building's AC system (which is designed on a per square foot basis assuming for a given number of people/computers/lights per square foot if the floor plan does not include a desk plan layout).
Architectural plans are like computer source code with a couple of differences: You only compile once.
Not scuba equiment, just a long hose that has one end out of the fluid.
In any case, I would love to work at such a place, if only to see the reactions on peoples faces when I tell them that I have to go scuba diving to do a disk swap! =D
God is dead -- Nietzsche
Nietzsche is dead -- God
Zombie Nietzsche lives! -- Zombie Nietzsche
That only works until you have a situation where you need to cut the green wire with the yellow stripe, NOT the black wire with the white stripe, in order to shut down your server before it explodes. That oxygenated fluid is pink, making colour detection damn near impossible.
Now, if you're willing to host an alien spaceship at the bottom of your datacentre, maybe they could lend a hand...
Endless arguments over trivial contradictions in books written by ignorant savages to explain thunder in the dark.
Raised flooring is useful for several reasons, moving cool air through a data center is only one of them. While requiring air to make severe turns to get out of the floor isn't optimal, most cabinets and the equipment in those cabinets is engineered with this in mind. Air is generally drawn in through the front of the cabinet and device and warm air blows out the back. Fans in the equipment pull the air in - the air doesn't have to "turn" on its own again (not that is really did in the first place). Warm air then rises after leaving the device where it is normally drawn back into the top of the AC unit.
Raised flooring also provides significant storage for those large eletrical "whips" where 30A (in most US DCs any how) circuits are terminated as well as a place to hide miles of copper and fiber cable (preferably not too close to the electrical whips). Where else would you put this stuff? With high density switches and servers, we certainly aren't seeing less cable needed in the data centers. Cabinets that used to hold five or six servers now hold 40 or more. Each of these needs power (typically redundant) and network connectivity (again, typically redundant), so we actually have more cables to hide than ever before.
Cabinets are built with raised flooring in mind. Manufactureres expect your cabling will probably feed up through the floor into the bottom of the cabinet. Sure, there is some space in the top of the cabinets, but nothing like the wide open bottom!
Anyhow, there you have the ideas of someone who is quickly becoming a dinosaur (again) in the industry.
I'm waiting for that day too! That way maybe the patent office will finally approve my perpetual motion machine.
It is not possible to build a computer that puts out zero waste heat. It is also not possible to build an LED light that puts out zero waste heat.
One further gotcha, the light that the LED emits (or the motion of the air that a fan is blowing) will be converted to heat if kept in a closed room. You can't win. Every watt you are burning in your datacenter will eventually require 1 watt of heat to be flowing out of your datacenter.
My amazing wife - Artist, Author, Philosopher - Laurie M
A similiar article can be found here.l es/Eliminate%20Raised%20Floors%20to%20Reduce%20Fac ilities%20Cost.aspx>
http://www.infotech.com/ITA/Issues/20051025/Artic
Is this Slashdot or Martha Stewart's website? I mean, is this the most moronic topic. Is Slashdot really stretching this far for something to say? Why not a topic "Do neutral colors in your cubicle help you take the shit that your know-nothing, MBA packing asshole boss shoves at you all the time?"
The world's burning. Moped Jesus spotted on I50. Details at 11.
Efficiency
LEDs are certainly better than flashlight bulbs.
But when a white LED delivers 15-19 lumens per watt, its about the same as a 100W incandescent and five times worse than a fluorescent. LEDs appear bright because they put out a fairly focused beam - not because they put out lots of light.
i'm more concerned about keeping my booze cool than hiding bodies. the bodies can be dissolved in caustic soda and flushed down the toilet
What ? Me, worry ?
We just did this last year. Power goes under the floor, data cables in trays by the ceiling.
"Almost every wise saying has an opposite one, no less wise, to balance it." - George Santayana
Personally, I think raised flors are obsolete in buildings with decently high ceilings. I'm more concerned to duct those heat exhausts away. Human accessways are more than enough for airflow. Raised floors are more for neat cabling which bitter experience has shown is best run in overhead trays.
Lip vibrations play the trumpet. The air is simply the medium through which the vibrations travel.
Spoon not. Fork, or fork not. There is no spoon.
Ok, it's pedantic time. Air (or anything else) can't make a true 90 degree turn. Two 45 degree turns, sure, it can make a bank shot just fine. Angle of incidence, people! :)
You are right, what goes in must come out in a closed system. Problem though is if the head is high, less goes in then original design may have called for and reduces the flow rate.
Bad boys rape our young girls but Violet gives willingly.
Really it all depends on the layout of the building and furnishings.
I installed a 200 client network in a rather old building that had been refurbished and we had no choice but to run our cabling through a raised floor because there was no drop ceiling and the building's owner denied us installing one or cutting the existing structure to run our conduits. So we put in a raised floor and ran our RJ45 through the walk ways between offices and dilbertcubes.
Adding in more clients will be easy as getting to the conduits is. It's when you run your main trunks under areas that will have funiture or dilbertcubes that you'll have issues. Plan, plan, plan and you'll have no headaches... er at least less headaches, this is still IT afterall!
As for air flow through a raised floor well... the idea of having problems with air flow at corners has been the bane of residential and commercial ductwork installers since the dawn of time. {smacks forehead in a moronic fashion}
There are only 10 kinds of people in the world. Those that understand binary and those that don't.
Hot air rises, cool air falls. The most efficient use of cooling would be to drop the air over the racks, the vents low from the ceiling so that the hot air would still rise up and be reclaimed.
Of course, with today's innovations in low-heat components, in-case cooling, and water-cooled racks, a truly efficient datacenter would use more than just under-floor cooling.
Definitely. Lowered ceilings for cooling, raised floors for wiring. Heat rises, so to have the cooling up high makes sense, and wires, well, fall down. Raised floors mean you can have thousands of metres of wires and not see them, trip on them or be able to hang yourself from them. Of course, with both a lowered ceiling and a raised floors, it's only applicable in a workspace for midgets...
Sig Appended to the end of comments you post. 120 chars.
I hope you mean inert as in conductively inert as well as oxidatively and corrosively inert.
Another big reason for raised floors is to handle wiring.
or pluming. I'm serious. (An a bit OT)
When I was at IBM's Cottle Rd. facility, now (mostly) part of Hitachi, they had just finished rebuilding their main magnetoresitive head cleanroom (Taurus). They took the idea from the server techs, and dug out eight feet from under the existing cleanroom (without tearing down the building) and put in a false floor.
All of the chemicals were stored in tanks under the floor. Pipes ran veritcally, and most spills (unless it was something noxious) wouldn't shut down much of the line. It was a big risk but, if what I hear is correct, people still say it's the best idea they had in a while.
I'd rather have someone respond than be modded up.
What is this "natural daylight" of which you speak?
Sounds exotic and danger filled. I'll pass thanks.
Cypherpunks: Civil Liberty Through Complex Mathematics. Those who live by the sword die by the arrow.
We would of course have to mandate an all-female staff, and that these fine women be most shapely.
That will dramatically increase cooling and virtually eliminate oxygen based fires.
Of course the hardware technicians will have to wear self-contained space suits to go into the room, and then those geeky types would then have a perfect way to really avoid the IT boss.
Zinc whiskers are a major hazard of raised floors used for cooling. Little shards of metal are not good for circuit boards.
"This mission is too important to allow you to jeopardize it." -- HAL
There are a number of slashdot visitors that do actually care about server room issues. The fact that you don't understand the need does not negate it's importance.
Large organizations rely on server rooms for their computing environment. Having a cobbled environment where the file server is on the 3rd floor, and the application server is in the janitor's closet, etc. is a recipe for disaster. Troubleshooting connectivity issues (among others) can end up costing more than the apparent simplicity of such a design.
Understanding ways to better cool the space that our servers occupy is important. And being able to do so in a cost effective manner is also important. The organization that I work in has one in-house server room (containing 60 racks of servers), and one 'co-located' server room (containing 72 racks of servers). Heat and power are the two killers. If we experience a 50% power loss (assume that one power grid is knocked out), do we have enough power to run AND cool the server room? If not, what percentage of my gear do I need to shut down in order to prevent overheating, without impacting critical business systems (like payroll).
If we can find a cheaper / better / more cost effective method for cooling that utilizes less power, or find a way to use the cooling systems that we have in a more efficient manner, is that not worth an article on slashdot?
IMHO, This is a valid topic.
Raised floor cooling was designed back when the computer room held mainframe and telephone switch equipment with vertical boards in 5-7 foot tall cabinets. The tile was holed or removed directly under each cabinet, so cool air flowed up, past the boards and out through the top of the cabinet. It then wandered its way across the ceiling to the air conditioners' intakes and the cycle repeated.
Telecom switching equipment still uses vertically mounted boards for the most part and still expects to intake air from the bottom and exhaust it out the top. Have any AT&T/Lucent/Avaya equipment in your computer room? Go look.
Now look at your rack mount computer case. Doesn't matter which one. Does it suck air in at the bottom and exhaust it out at the top? No. No, it doesn't. Most suck air in the front and exhaust it out the back. Some suck it in one side and exhaust it out the other. The bottom is a solid slab of metal which obstructs 100% of any airflow directed at it.
Gee, how's that going to work?
Well, the answer is: with some hacks. Now the holed tiles are in front of the cabinet instead of under it. But wait, that basically defeats the purpose of using the raised floor to move air in the first place. Worse, that mild draft of cold air competes with the rampaging hot air blown out of the next row of cabinets. So, for the most part your machines get to suck someone elses hot air!
So what's the solution? A hot aisle / cold aisle approach. Duct cold air overhead to the even-numbered aisles. Have the front of the machines face that cold aisle in the cabinets to either side. Duct the hot air back from the odd-numbered aisles to the air conditioners. Doesn't matter that the hot aisles are 10-15 degrees hotter than the cold aisles because air from the hot aisles doesn't enter the machines.
Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
Move the computers to a colder place.
Credo sim. - I think I am.
Well since its cold most of the year, except from May - Aug, here's a solution that would work most of the time.
Just have a vent that sucks in air from the outside to the bottom of the server room and a vent on the top of the server room that blows out all the hot air.. You probarbly don't even need a fan to circulate the air since the hot air should rise to the top and the cold air should creep to the vent and make the entire room cold...
Laminar flow results in poor mixing of the fluid. This lack of mixing will cause the portion of the flow not in contact with the heat source to remain cold. Turbulent flow actually results in better cooling (but it takes more work to move the fluid).
Many years ago, we moved into a new building where we were able to build a new computer room. A few months after we moved in, a sewage pipe clogged up and sewage started backing up into the computer room. We had water (or liquid at least) rising up under the raised floors to the point where it was starting to get into the power that was down there. I finally had to shut down the whole computer room to prevent it from going poof.
The maintenance people where able to fix the problem before the water got too high, but we had to have the space under the floors cleaned before we could start up again. That was real fun to explain to the COO.
What sort of drugs are you on? Or rather what sort of drugs are you supposed to be on that you are not taking?
A place to hide the bosses body and won't stink up the place :P
What kind of beer are we talking about?
"The problem lies with larger datacenter environments. Imagine a room the size of a football field. Along the walls are rows of air conditioners that blow cold air underneath the raised floor. Put a cabinet in the middle of the room and replace the tiles around it with perforated ones and you get a lot of cooling for that cabinet. Now start adding more rows & rows of cabinets along with perforated tiles in front of each of them. Eventually you get to a point where very little cold air makes it to those servers in the middle of the room because it's flowing up through other vents before it can get there."
Perhaps you're referring to difficulties in retro-fitting, but I work in a data center this size which was purpose-built by Tyco with 24" raised floors and doesn't have a bit of problem moving enough air through the space.
One of the design considerations that I was intrigued by when I first started working in the place was a layout that included alternating hot & cold rows. Cold rows have perforated tiles and show the front sides of the server machines on both sides of the aisle. This is the "intake" side of a properly built machine, so the floor feeds cool air into the machines. Hot rows has no perf tiles, but instead airhandler inlets above the aisle where the air conditioners draw in the warm exhaust air from all the machines whose rear is facing the aisle on both sides.
It's actually a strange environment to work in going from hot to cold rows while working on machines, but it seems to work well. The room holds at a steady 60 degrees Fahrenheit despite 40 rows of equipment working hard at reversing the cooling effect.
It's amazing how some people are so retarded. Raised floors should only be for cables. Not your main source of duct for cooling. Hey guess what? Heat rises. Put return grills above the server and dump the supply from across the room.
Your not making cold air, your removing the heat!
Well, if someone else made a system that was similar I'd mention them. Since no one does, it makes it kind of hard, doesn't it?
but didn't taco misspell "herre" ?
Note that I'm not calling the parent poster stoopid, but rather the design of forcing cold air through the *floor*. As the parent here notes, cold air falls. This is presumably why most home fridges have the freezer on top.
I was most surprised to read this article. I've never worked in a data center, but I have worked in semiconductor production cleanrooms, and given the photos I've seen of data centers with the grated flooring, I guess I always assumed the ventilation was handled the same way as in a cleanroom -- new air in from the ceiling, old air whisked away through the floor. (This ensures that any particles, which will naturally fall if heavier than air, will be sucked out of the room.) Note that this is obviously *not* a passive system designed to use convection, but rather an active system using lots of fans.
While a passive convection system with the cold pulled up from below is a nice theory, you can run into the same problems others have pointed out -- what if the bottom units suck in all the cold air? The top units are left too warm.
Meanwhile, if you drop cold air from above, sure, the top units might suck a lot of that in -- but any cold air that isn't sucked in will naturally continue to drop relative to warmer air, ensuring that the lower units are not cooked. If you want to be especially careful about it, you could route all the cold air outputs towards the perimeter of the room and put the uptakes in the center of the ceiling to ensure a vortical flow.
Just my ¥2.
"What in the name of Fats Waller is that?"
"A four-foot prune."
I'd say use Oil instead, like the guy with the aquarium computer, because it's cheaper than the $1000/L for florinert. But with the current trends for oil that may not hold up long.
Even people that believe in pre-destiny look both ways before crossing the street.
Except for the concrete dust... if you were to use a slab, I'd be sure to coat it with a very robust membrane of some sort.
$0.02 (CDN)
I spent the first 8 years of my professional life stuck working in NOCs with standard raised flooring, the cooling was just one of the many things it was needed for.
Examples:
Wiring: Not everyone likes to use overhead ladders to carry cables around. In the Army we had less than 50% of our wiring overhead, the rest was routed thru channels underneath the raised flooring.
HVAC Spill protection: Many of our NOCs had huge AC units above the tile level, and these things could leak at any moment. With raised flooring the water will pool at the bottom instead of run over the tiles and cause an accident. We had water sensors installed, so we knew we had a problem as soon as the first drop hit the floor.
If the natural airflow patterns are not enough for a specific piece of equipment, it does not take a lot to build conducts to guarantee cold air delivery underneath a specific rack unit.
The one thing I did not like about the raised floors was when some dumbass moron (who did NOT work within a NOC) decided to replace our nice, white, easy to buff tiles, with carpeted tiles. 10 years later and I can't still figure out why the hell would he approve that switch, since our NOC with its white tiles looked fricking gorgeous just by running a buffer and a clean mop thru it. The tiles with carpeting were gray so they darkened our pristine NOC.
I bet many of the people against raised flooring are land lords that don't want to get stuck with the cost of rebuilding flooring if the new tenant does not need a NOC area. I have been to a NOC in a conventional office suite, they basically crammed all of their racks into what seemed to be a former cubicle island. The air conditioning units were obviously a last-minute addition and it looked like the smallest spill would immediately short the lose power strips on the first row of racks in front of them. Shoddy as hell.
Pedro
----
The Insomniac Coder
iirc its very very difficult to breath under even a fairly small depth of liquid unless the air is presurised to match the water pressure
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
Raised flooring is great when the AC drain clogs and the air conditioner starts leaking water. It can be building up down there for days but you'll always stay high and dry! The cables don't seem to mind either.
I don't think it is a very good idea to hide your cabling, either power or data. Raised floor just becomes a place to hide things and collect dust, and makes it much harder to make changes. I've seen shallow raised floor which could not be re-seated after it was pulled because of the volume of cable underneath. I've also seen a raised floor environment that became a hazard when the Loma Prieta earthquake popped up every fifth tile or so.
I believe the idea of hiding cable came from early IBM promotional photos that showed a beautiful sea of white tile with an IBM-logoed monolithic rectangular solid standing there in all of its phallic glory. The purchasers, who were not the operators, came to see this as a natural way to install and manage hardware. In my high school days I saw a Sperry Univac 1107 that was not only mounted on raised floor, but actually had components installed in decorative columns that matched the building deco, kind of like a light switch would be in an office -- the whole room became the computer.
Cabinets also make little sense. Why make it hard to connect, disconnect, mount or dismount your hardware? The telcos have been using open racks since the beginning of time -- a much more efficient way to handle hardware that changes or must be inspected frequently.
Power and data should run in separate ladder/tray overhead, where it can be seen and pulled, inspected or added to easily. 20A or 30A power outlets installed in the tray (or overhead duct dropped from the ceiling where electrical codes require) make it easy to attach your cabinet (or better, relay rack) power distribution.
In my line of work the whole point of raised flooring is not for use as an HVAC plenum, but for running cables. Having even a 6 inch raised flooring area can really be a godsend when you are constantly rewiring a lab area.
I've seen these systems used in makeshift or closet "datacenters" where servers (and other heat-producing equipment) were placed into a small space like a closet with nonexistent or inadequate cooling. Essentially, they put the evaporator in the same room as the heat source, with only coolant lines leading out to the condenser. They eliminate the need for a duct system, and they let convection currents do most of the work.
Vendor 1
Vendor 2
Furthermore, if you speak to the insiders at most of the modern equipment manufacturers, they will tell you that the benchmarking processes are now done on solid, non-raised floor environments. The assumption is tonage of cooling is provided at the intake, which is not located at the bottom of the larger machines, but at the front or back. The hot aisle/cold aisle methodology is still the only viable means for cooling high power density equipment in a large datacenter environment. The only remaining issue is how to get rid of the hot air, and clearly the simplest initial design criteria should be high ceilings (hard to find in datacenters). Outside of that, high velocity air, specially designed air returns, or compartmentalized racks with dedicated air returns are alternatives. In most flow dynamic studies, you find raised floors are riddled with statification, hot air being delivered back into the intakes of other gear, whereas in non-raised hot-aisle/cold-aisle, this problem magically goes away...
The low cost BUT viable solution I've used...
All must be done - or no go!!! You can't pick and choose...
1. Go with concrete floor that is certified SEALED.
2. Arrange racks in the same row arrangement...i.e., all in parallel.
3. At each end of the racks - place your coolers - usually 20 tonners...that's where the heat pickup occurs.
4. Have those coolers dump their recycled air via the ceiling throughout the room.
The next steps are extremely important...
5. For every set of entrance/exit doors to the room, there must be a room between those doors and the main corridors outside - i.e., to exit one must exit from the data room through doors into a small adjacent room and then through doors again to the main traffic areas outside.
6. This buffer room between the data room and the main traffic corridors must have it's own 3-5 ton cooling unit - usually in the ceiling.
Why?
1. Sealing concrete floor reduces moisture seepage from the ground...
2. Parallel rows allow for a air circulation pattern to and from coolers...
3. Obvious postion for the coolers...they create the cycle and flow...
4. Obvious...
5. Creates an air exchange buffer for treated, semi-treated and untreated air.
6. Pre-cooling of air in the adjacent room before it seeps through the doors into the dataroom itself prevent ice buildup on the coils of your coolers in the data room.
There's nothing more irritating than having moisture brought in via warm outside air directly creating ice buildup on your coolers. Thus you need a cooled buffer room with it's own moisture removal piping.
=8-)
The above design works quite well for a 100 rack / 1000-2000 server room relatively squarish in configuration. Includes EMC/Netapp cabinets...
=8-)
Well, you're close. You are correct that the answer lies in a "hot aisle/cold aisle" configuration. The difference is, it works better when the cold air is coming up from below the raised floor tiles.
Why? You must keep in mind, you're not trying to pump "cold" air in, you're trying to take heat out, and as Mother Nature knows, heat rises. So why not harness the natural convection of heat, allow it to flow up to the ceiling, and have some "perf" ceiling tiles and use the space over the ceiling tiles as your return plenum. Thus, you end up with a positive pressure beneath the raised floor, your heat load in the data room, and your negative pressure over the ceiling tiles leading back to your CRAC units.
I assure you it works fabulously in our 2 year old data center at a major financial company. The other advantage to raised floor is, you don't have to worry about water being overhead. No one wants a condensor water, chilled water, or glycol pipe bursting over a row of server racks. But, put your power whips in liquid-tite conduit, use cable racks for the CAT5 and there's no problem if you have a leak. The leak detection ropes pick it up and you can contain it before it becomes a problem.
The original concept was always space for wires and PIPES for the water-cooling. People think that fluid-cooling is so new and keen; mainframes of the 1960s were water-cooled because nothing else would do. Refrigeration fluids make things cold enough to crack old-fashioned PC boards, and have more condensation besides.
Yeah, now it's a tourist attraction in Egypt :)
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
well now... so much for light reading.
The world according to SComps
and possibly liquid cooling where the radiator is outside the building...
And move the data centers to Canada where for 7 - 8 months a year cool air is FREE! Think, if you open up a data center in a colder prarie province the incoming air will be so cold it won't mater how many 90% turns it has to make. You could also pump the heat to the rest of the building.
Raised flooring works where the cabinet placed on the hole in the floor is required to be slightly pressurised. A lot of older network equipment cabinets and current closed network equipment cabinets, have no perforations to let air escape and the airflow moves from bottom to top (doesn't matter how the switches/ routers move air about themselves)the hot air always goes out the top.
Contrast that with modern servers that move air from front to back through the server chassis, in the HP cabinets you must have the perforated / grill front door on the rack to allow the server to pull air through it. You must use the correct type of cabinet for the servers it's specified by HP.
Some big-iron servers / Suns and whatnot require airflow from the bottom of the server (as it is in it's own chassis / cabinet) and this is where having a raised / pressurised floor system is required.
air can turn corners but with each corner there is additional friction, and heat. Not to mention noise. Two many corners equal wasted energy. I work with mechanical engineers all day, trust me they hate corners especially 90 degree ones
Conduction moves a lot of heat, which is why copper or aluminium heatsinks are attached to hot components. Insulation as described above is there to slow down conduction, so is not what you want when the air outside of the box is likely to be cooler than some of the air inside of the box.
Heat transfer by convection depends on surface area, fluid velocity and the temperature difference between the surface and the fluid. This is why heatsinks have big fins and fans. Hot air will rise if it has somewhere to go (it may have trouble getting out of a case) and cool air will come in, but in a lot of cases this isn't enough so you need to force the airflow. A rack with no fans inside any components would generally act as a chimney - cold air in the bottom and hot air out the top.
If you can pump a lot of dry cold air in the bottom and exhaust hot air out the top it may make sense to insulate the rack and have it as effectively a mininture server room, but with a minor airconditioning failure you would have an oven, which is one reason rack cabinets are rarely sealed and are not insulated.
Each time you send air around a tight corner you lose velocity, and thus can shift less heat from convection. Dead spots where air pools only give you small amounts of heat transfer as you have to heat and expand the air before you can get cooler air coming in, and unless you have surfaces at very different temperatures you can ignore heat loss from radiation completely.
OTOH, LED bulbs are very efficient. I think even flourescents run at 40% efficiency compared to a perfectly efficient visible light source.
Computers are nowhere near perfect efficiency. If they were, then the primary power consumption would be in state changes rather than (as I understand it) internal resistance. Obviously, less power consumed means less heat that has to get transfered out. You can win in that you have less heat to dissipate.
...and allows the spys to crawl from one end of the building to the other.
TileFlow is excellent for most conventional datacenters and has served us well. Best practice in a conventional datacenter is to use TileFlow to ensure positive pressure and appropriate distribution (don't forget to model all your underfloor blockages), set up cold rows and hot rows, and then use a drop ceiling as a plenum with strategically located grates to pull the hot air back into your CRAC units. The only problem, as others have pointed out, is that it's only a 2D model presently and you really need to start modelling your load in 3D when you get past around 12kW/rack.
We've speculated that if we were to start all over again we'd skip the raised floor and do a bi-level drop ceiling with one level being cold air distribution to cold rows and the other level being the hot air return. Let cold air fall and warm air rise, and augment it all with XDO's from Liebert.
I guess I really missed the train on this one as far a karma points are concerned, but here it goes, anyway.
In the current data center design paradigms that I have seen, the raised floor is about as useful as tits on a boar pig. Most of the data centers I have seen have consisted of a raised floor topped by a server rack that is either sealed at the top for security, or open to the room as a whole for cooling. The whole mess being punctuated by overhead cable racks whose sole purpose is to cause contusions and the rapid ejection of expletives from the over-tall. The net result is a server room that is too eff-ing cold for the average human to tolerate, while being only partially effective in its' intended design purpose.
However, The raised floor can be useful if the design is correctly laid out. Use the principles of "Naval Damage Control and Firefighting" your advantage.
After seeing how airflow is controlled on ships at sea, you will come to understand that the proper design is to have a positive pressure ventilation system under the raised floor, and a negative pressure ventilation system in the overhead. (ceiling, above the drop tiles, whatever you land lubbers call that stuff over your collective, office-bound heads.) The raised floor should be joined to the overhead by a simple ducting system consisting of sealing the top of the server rack to the ceiling using whatever is available (sheet metal, cardboard, left-over swag from E3 1996 or Sci-fi-con-whatever-1992). This way, the cooled air from the chillers can be forced under the floor, through the racks, and up into the overhead where it is exhausted. Hell, if you're an efficiency freak, use the exhausted server air the A/C source for the human occupied portions of the data center. A constant flow of 50-degree air makes 'puters happy, and it makes CBLFs shiver. The "too many corners in a raised floor" thing is a red herring.
Although an ornately designed under-floor ducting system can and will lead to un necessary inefficiencies in the cooling of server racks, by using the KISS principle (keep it simple, stupid), the same basic logic that works on every commercial transport, pleasure craft, or military ship in the world can work in a server room too. Two simple plenum spaces connected by the duct of the server rack is in fact, the MOST efficient way to cool a room full of number-crunching toaster ovens.
== That terrible green-green grass, and violent blooms of flower dresses, and afternoons that make me sleepy.==
I've just worked for a couple of days in a server room like that... wich used to house mainframes, enormous room btw. more than 1000 m... It is now totally rebuild and used for "normal" racks. They don't put the AC units along the walls anymore, they put them in every row of racks. There is something like 10 tiles (6 m) max. between AC units.
The solution could be quantum computers
They should be less power hungry and less power means (also) less heat.
Maybe Computers will never be as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]
The solution, IMHO, is to have a much more powerful fan pushing that air around. You don't really need more AC, just more pressure...
Alternatively, you can make the vents in the middle much larger than the rest to compensate.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
that'd apply if you're forcing air into a pipe and watching it come out of the other end. the issue is that if you're forcing air into, say, an underfloor system that's full of different shapes, air passages, etc that the airflow will tend to the path of least resistance, and you'll get less airflow in pockets, which might cause problems.
Raised flooring systems were designed to accommodate the environmental requirements of mainframe computer technology in the 1960s. The technology of the time required large copper I/O cabling interconnecting the cabinets, hardwired power cables, a glycerin cooling infrastructure, and bottom-to-top airflow.
Although environmental requirements for the technology installed in server rooms changed, the perceived need for raised flooring systems remained. Modern server room technology utilizes small flexible interconnecting cabling, standard 120V power cabling, and forced front-to-back airflow. In today's server environment, raised flooring systems have simply become an excuse to adopt poor cable management and hide the cabling mess.
An argument for the continued use of raised flooring systems is the delivery of chilled air. However, raised flooring is not a good air delivery system, since the entire floor cavity must have positive pressure to act as an efficient distribution plenum. Flooring systems cannot be adequately sealed for this process to work efficiently and, in real-world IT operational activities, floor tiles are removed or relocated for extended periods of time. Furthermore, most of today's server technology benefits from a front-to-back airflow, which is counter to the airflow delivered by a raised flooring system.
The efficiency of overhead ducting of chilled air is far more likely to deliver air where it is needed in modern server rooms, all at a reduced cost.
The one thing I did not like about the raised floors was when some dumbass moron (who did NOT work within a NOC) decided to replace our nice, white, easy to buff tiles, with carpeted tiles. 10 years later and I can't still figure out why the hell would he approve that switch, since our NOC with its white tiles looked fricking gorgeous just by running a buffer and a clean mop thru it. The tiles with carpeting were gray so they darkened our pristine NOC.
Very odd. In the (brief) time I worked in a raised floor NOC in the Marines, the only access we had below the raised floor was with suction based handles that you pumped with your thumb to lift a tile. I can't quite imagine a more functional and efficient method that could be used for carpeted tiles. I doubt velcro or an equivalent would be much use for any extended period of time.
No conformist ever made history.
flourinert is several hundred dollars per liter...
I saw (online) someone once try to liquid nitrogen cool with flourinert. They hollowed out a cooler, set the computer in, put in a passive heat exchanger...
Worked great until they realised that at liquid nitrogen temperatures flourinert gets so viscuous it becomes a gel.
At $500 for the amount they used, this was a fairly expensive lesson to learn hahaha.
I am disrespectful to dirt! Can you see that I am serious?!
Our building was designed principally by telecommunications and IS professionals about seven years ago. We had a real architect for legal compliance, but he was nearly constantly baffled by our requirements. It has a large raised floor area, about 70 by 35 feet.
Originally, there were bus & tag cables (about as thick as a fat man's thumb) under the floor as well as flood sensors and huge power lines for feeding the mainframe peripherals. The under-floor plenum is pressurized with filtered air so that cooling can be supplied anywhere in the room by simply replacing or re-orienting floor tiles.
We were only planning to run the mainframe until about 2001, and that worked out according to plan. Today, in the space where the mainframe's many refrigerator-sized boxes once stood, we have racks of 2u and 4u servers. We still have the flood sensors, mainframe-class UPS, and pressurized plenum. We also have strategically placed drag lines so we can pull new wires from various useful places without lifting more than two tiles at a time.
In the Real World [tm] the vast quantity of cat six cable required to give us mainframe-class reliability with commodity hardware is larger in both volume and mass than the mainframe cables ever were.
Unless you are going wireless, or you have a 1960s era computing infrastructure (25-pin RS232 anyone?) the number of wire runs required to serve x number of desks does not decrease significantly when you change server technologies. In fact, given that new installations typically use all home runs of twisted-pair ethernet, the amount of wiring will typically increase over that required for old-school etherhose (10b5) or coax/twinax/LAT dumb terminal infrastructures.
Trust me on this one, I've been building computer infrastructure since 20 mA loop days!
The zero humidity from the winter air would cause such horrendous static electricity that the machines would most likely be dead in no time. Humidifiers are your friend when cooling a DC with outside air.
Using the cold of outside is not uncommon. Doing this by dumping unconditioned outside air into the space is. An Air-to-Antifreeze heat exchanger ("dry cooler") is used outside and the cooled antifreezse is pumped to the inside to do the cooling.
Evaporative humidification is another way of getting "free" cooling.
1U servers also have this kind of problem, and it's not clear to me that there's an obvious solution, other than perhaps building a cooling system that with a bunch of 1U or half-U slabs cooled by heat-pipe or chilled water that blow air into the box above them, which would be complex and a big hassle.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
During the years that was going on, we had a guy in our sales group who was a wine expert and also part of a small winery with some friends, and we'd have ~weekly wine-tasting sessions in the evening after work with whatever he'd found that was interesting that week. (Had to be more than one bottle - "Two or more bottles means you're doing a tasting - one bottle is just drinking.") So when we got the ugly AC box in my lab, it was obvious that we ought to do white wine one week - the holes in the front were just about right for two bottles.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Some planning is in order for football field-sized datacenters.
Distribute your AC units throughout the space in the first place.
Apparently, fluid dynamics and thermodynamics are not very well understood around here if you had to make that post.
My good friend who is also an audio engineer at Busch Gardens, Tampa, FL gets a couple of cases of free beer every week by his employer.
He said years ago they used to be able to actually drink on the job, but apparently they ran into some liability issues with that one.
I'll never forget going to my community college in Orlando when they were starting their recording program.
They moved us from room to room because of our noise (we recorded a lot of metal) and we were next to a computer lab for a few months. They hadn't found a suitable place to set up a permanent studio for the program yet.
Well, to record we had to shut off the HVAC/AC so that the rumble wouldn't raise the noise floor of the recording. Needless to say, the computer lab people next door were PISSED every time we felt the need to lay down tracks!
Libertas in infinitum