Slashdot Mirror
10 IT Power-Saving Myths Debunked
snydeq writes "InfoWorld examines 10 power-saving assumptions IT has been operating under in its quest to rein in energy costs vs. the permanent energy crisis. Under scrutiny, most such assumptions wither. From true CPU efficiency, to the life span effect of power-down frequency on servers, to SSD power consumption, to switching to DC in the datacenter, get the facts before setting your IT energy strategy."
Myth No. 6: A notebook doesn't use any power when it's suspended or sleeping. USB devices charge from the notebook's AC adapter. Fact: Sleep (in Vista) or Hibernate mode in XP saves the state of the system to RAM and then maintains the RAM image even though the rest of the system is powered down. Suspend saves the state of the system to hard disk, which reduces the boot time greatly and allows the system to be shut down. Sleeping continues to draw a small amount of power, between 1 and 3 watts, even though the system appears to be inactive. By comparison, Suspend draws less than 1 watt. Even over the course of a year, this difference is probably negligible.
um... Hibernate != Sleep. Hibernate in XP saves the RAM to the Hard Drive, and powers off. Suspend keeps RAM powered....
The above comments are not guaranteed to make sense to anyone other than the author...
That depends if your system has been tuned to boot in 5 seconds.
Or if it can return from suspend-to-ram nice and quick.
If you're booting those servers diskless with PXE and NFS, the boot time should be negligible. I should imagine the trick would also be to bring additional resources online before you are the point that you must tell users to wait while the server boots. The magic would be in predicting near-term future use...
Sorry for the thread hijack, but I decided to post this link as soon as I saw the links to all 4 pages of the top 10 list.
http://www.infoworld.com/archives/emailPrint.jsp?R=printThis&A=/article/08/10/06/40TC-power-myths_1.html
He's getting rather old, but he's a good mouse.
I like how this plays with the following assertion filed under "Myth No. 9: Going to DC power will inevitably save energy."
"New servers have 95 percent efficient power supplies, so any power savings you might have gotten by going DC is lost in the transmission process."
So, when it suits his argument, power supply efficiencies range from 50-90% efficency, and are kept hidden by manufacturers. Then, when that doesn't suit his argument, all of a sudden power supplies are at least 95% efficient, and everyone knows that.
I call shenanigans!
FTA:
Hibernate mode in XP saves the state of the system to RAM and then maintains the RAM image even though the rest of the system is powered down.
They must be using a different version of XP than I am... When I 'Hibernate' my laptop, it dumps the RAM to a file on the hard drive and then powers off completely. When I 'Stand By' my system, it keeps everything in RAM.
Maybe they have SP4...
He's getting rather old, but he's a good mouse.
1. Spinning up and down hard drives: as discussed in plenty of places, including here on /. I believe, you can dramatically reduce the life of drives when you cycle them due to mechanical wear-and-tear. Laptop drives are designed for a lot more cycles because they're intended for this, but if you do it constantly even they'll die sooner or later. Server and desktop drives, OTOH, will die MUCH sooner. Is it really worth some extra power in a server farm in exchange for dying drives and their associated cost, including the increased possibility of data loss?
2. LCD Backlighting: Same as above--cycling power on any kind of discharge lamp dramatically reduces its life. And while LED backlighting is VERY efficient, AFAIK there are still major issues with color rendering--if there weren't, we'd be replacing regular lighting with them left and right. There's also the cost problem, particularly with the looming major shortage of gallium and indium. I think the only reason people don't talk about it more on laptops is because they're considered to have such a limited life expectancy since they're not expandable; now that desktop monitors are becoming more ubiquitous, I think we'll be seeing more talk about it.
3. SSDs: Their disadvantages have been talked to death here and elsewhere.
Mike
If you are using electric heat, chances are you don't live in a cold climate and pay for air conditioning for much of the year negating any "savings". Here in cold-balls Canada, EVERYONE has centeral heating; it's too expensive to use electricity. That being said, I do agree that datacenters' heat should be used to heat useful things (office bldgs, like you suggest).
Copyright 2010. All rights reserved. This comment may not be copied in any way including, but not limited to caching.
Well I live in Canada, and most people I know use electric heating. Yes, central electric heating is great, and actually cheaper than oil around here. (Montreal area)
Out-right potentially wrong: no one cares if a customer is made to wait for a server to boot to get served. That's not a generalization to be made lightly... It is true, though, that suspend-to-ram has not received the attention it deserves in the data center. A great deal of server-class systems and options are not designed to cope with suspend-to-ram, and thus you must be careful banking on this. The industry should correct it, but a facility can't bank on it yet (just put pressure on your vendors to make it so...)
Straw-man: A supposed 'myth' that leaving on LCD monitors is fine for energy savings, with the remarkable clarification that being off saves more power... Who would have thought.
Other straw-man: You will unconditionally save money by rapid upgrades to the latest efficient technology. I don't think anyone is foolish enough to think compulsively following any technical treadmill will lead to any overall financial gain..
XML is like violence. If it doesn't solve the problem, use more.
Probably the biggest and most annoying/disrupting power saving myth is Daylight Savings Time. Every year, the power companies announce that they don't notice any change whatsoever in power consumption.
Excuse me, but please get off my Pennisetum Clandestinum, eh!
Yea, I don't know who wrote that bit in the article, but they're just dumb. If you run any kind of system with a load balancer in front of it you can easily script starting up additional machines as soon as your monitoring says you reach 90% capacity.
Actually VM tech goes a long way to doing that anyway, provided you've a vaguely good concept of workload fluctuations.
I had the same problem. So I installed a patch (http://support.microsoft.com/?kbid=330909) from Microsoft. Essentially it's looking for a continuous free area on your HD to save your RAM to. I believe the fix is to disable this "feature".
Google developed their own power supply
Actually, Google's point was that they wanted motherboards that ran on 12 VDC only. PC power supplies are still providing +12, -12, +5, -5, and +3.3v. Most of those voltages are there for legacy purposes, and DC-DC converters on the motherboard are doing further conversions anyway. So there's no reason not to make motherboards that only need 12 VDC. Disks are already 12 VDC only, so this gets everything on one voltage. This simplifies the power supply considerably, and avoids losses in producing some voltages that aren't used much.
But Google wasn't talking about using 12 VDC distribution within the data center. The busbars required would be huge at such a low voltage. They were talking about using 12 VDC within each rack. Distribution within the data center would still be 110 or 220 VAC.
Tip number seven talks about battery conservation in LiIon vs. NiCd batteries. Um, laptops haven't used NiCd's in years. Their predecessors, NiMH hasn't been used in laptops in quite a while either.
Can you even buy NiCd's anymore, for any device? I can't remember the last time I saw them in an electronics store.
SirWired
I know a total of 5 people who don't use natural gas for heating, and 4 of them use propane as they're so far out of the way the gas network doesn't reach them. only 1 guy uses non-central (heating controlled on a room by room basis) electric. In terms of raw dollars-per-joule, gas is a way better proposition. even after the latest electric rate jump (from 6 cents to 9 cents per KW-hr), gas is still about 1/3 the cost of electric heat.
upon the advice of my lawyer, i have no sig at this time
"Myths" 1-4 are true
I haven't heard "Myth" 5 since 1999.
"Myth" 6 is also true.
When a system suspends to disk, it uses no power.
When a system suspends to RAM, it uses VERY LITTLE (strobe) power, and you can configure wireless adapters and USB devices to be turned OFF when you suspend to RAM. (I'm using "suspend" for both cases - FUCK the sleep/suspend/standby/hibernate/whatever for 2 different states bullshit.)
A laptop's charging circuitry and ac adapter is independent of the power state, so of course the adapter is going to be running all the time to keep the battery charged and power the system.
They admit that the power use is negligible when suspending to disk or RAM (and probably running 3 wireless mice that don't turn off, in an idiotic attempt to boost their non-existent numbers).
They don't admit that they couldn't find anyone who thought that the green light on the power brick meant it was off and using no power.
Myth 7 is true as well.
NiCd batteries do suffer from memory effects, and their capacity decreases over time. Conditioning a NiCd will remove the memory effect, but will not restore lost capacity due to general age.
NiMH batteries have much less of a memory effect, and less of a capacity loss through age. There is no need to condition a NiMH battery. Just drain it fully and then recharge it in a cheapo dumb charger, or buy a better charger (which will likely advertise a battery conditioning feature anyway).
LiIon batteries do lose capacity over time. If a cell (the smaller cells, not the 6 or 9 individual batteries in your laptop's battery) is completely depleted, it won't recharge again. If a cell is overcharged (or overheated), it will pop, and you've lost that capacity., and maybe your pants + laptop if the damn thing catches fire.
"Myth" 8 is true, as long as you remember that the hard drive is just one item drawing juice in a system.
"Myth" 9 is true, as long as you do it right.
The problem with DC is that you lose power over distance. Converting from AC to DC in a specific box can be more efficient than any server power supply, more reliable, and output cleaner power.
The issue is distance.
"Myth" 10 is true. "As soon as possible" means "When the servers are on fire or when we're 6 months overdue on our replacement cycle, whichever comes first...maybe". Energy costs are through the roof, and it makes sense for that to be a high priority in determining what you buy. You may even want to buy a more efficient server/power supply/switch/UPS/line conditioner EARLY if your budget allows for it. We all know that any money sitting around unused will get grabbed up by someone else, so use it or lose it.
That replaced equipment still has value (especially if you replace it early), and if you can resell those, you'll usually wind up ahead. in the long run.
I would guess you either have a piece of hardware or driver that isn't fully ACPI-compatible or you don't have drive space for the hibernate file.
upon the advice of my lawyer, i have no sig at this time
I'd recommend a Cisco PIX. If that's too expensive, get a decent consumer router like the Linux-based Linksys, then run DD-WRT on it. It doesn't make sense to run firewall software on an old PC at home anymore unless it's a power-sipper like a VIA running off flash.
Gamingmuseum.com: Give your 3D accelerator a rest.
Well I live in Canada, and most people I know use electric heating...(Montreal area)
To be fair, when snowraver1 said 'Canada', I think he actually was referring to Alan Fotheringham's 'TROC'(The Rest Of Canada), i.e., the unwashed masses outside of the 401 corridor.
Here in Alberta, as in much of western TROC, it's good old natural gas.
db
I am literally 3000 tokens away from the chaotic crossbow --Stephen
Disks are already 12 VDC only
Actually HDDs use +12v for the motors and +5v for the electronics. If you have a 3.5" FDD it only uses 5v. If you don't believe me try swapping the yellow (12v) and red (5v) wires going into the power connector on your HDD some time ... here's a hint, the smoke you see coming off the electronics isn't from putting 5v into something that expects 12v (note if you're really dumb enough to do this I won't be held responsible for ruining your HDD).
Windows is a bonfire, Linux is the sun. Linux only looks smaller if you lack perspective.