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When Does Powering Down Servers Make Sense?
snydeq writes "Powering down servers to conserve energy is a controversial practice that, if undertaken wisely, could greatly benefit IT in its quest to rein in energy costs in the datacenter. Though power cycling's long-term effects on server hardware may be mythical, its effects on IT and business operations are certainly real and often detrimental. Yet, development, staging, batch processing, failover — several server environments seem like prime candidates for routine power cycling to reduce datacenter energy consumption. Under what conditions and in what environments does powering down servers seem to make the most economic and operational sense, and what tips do folks have to offer to those considering making use of the practice?"
Put redundant/failover servers into a sleep state and enable WOL.
It's pretty much up to your business....what must run 24/7, what systems are likely to get accessed in off hours, and how likely is that, and how critical are they? With redundant systems, can there be any downtime while they are powered up, or should it be immediate failover? If you use virtualization the redundancy should be easier to manage in many cases...you may be able to immediately offload to running systems and power up backup systems and then bring the VMs up there.
It's hard to get very specific without knowing your business and what you are running and what the needs are.
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.. your business doesn't depend on it.
Seriously .. powering down failover boxes or something like that is not wise thing to do.
Imagine in some fucked up situation, when your main systems goes down... you can't boot failover servers for some reason ... long fsck, or whatever.
You can power off the servers that aren't critical .. Why question on slashdot for that ?
Logic anyone ?
When you're sure you don't need it to come back up.
You don't make the poor richer by making the rich poorer. - Winston Churchill
How many of us have servers that don't need to be live? Yeah, I guess there might be a development server, but that assumes that you're not developing. There could be a failover server that does nothing when the primary hasn't failed, but in that case you'd want to be damn sure that the failover will come online without difficulty when it needs to.
It seems to me like it would be a pretty rare case when this is applicable. I'd sooner be interested in asking, can they build servers that can selectively power down subsystems that aren't currently in use, sufficiently enough that there's no serious harm. For example, I'd consider putting some of my fileservers' hard drives to sleep over night, but I'd still want the server to be available and the drives to spin back up if I log in from home and need access.
Mostly, I'd say that if you have servers that you don't need to be live, you might not be using your servers efficiently. It may be worth looking into setting up some kind of VM server with various images that can be brought up on command. But hey, if you do have a server that you can turn off without causing problems, go for it.
It's not 03:00 everywhere on the planet nor is it sunday either.
What kind of UPS does that? If the batteries are already charged, what would it be doing with the power that's not consumed by the devices - does it also act as a space-heater?
The ratings for UPS's - and any other power supply - are peak loads, if the UPS is being used at 100% capacity.
"Servers that sit in idle state for long periods of time are the top candidates for powering down between uses."
Then virtualize it or combine its function with another server. I see this part of the article as a bad example. It starts by saying that virtualization has helped, and then uses an example that virtualization would solve, NOT power-cycling.
Maybe its just me, but when I think of a server, I think of something important that is running, that needs to be accessible on something other than a glorified desktop. If it is important, then it cannot be turned off.
Bearded Dragon
You're assuming the web servers are for an international service.
If it's a website, it's international, wether or not the actual products and services are available internationally.
My guess is that managing energy consumption by powering down servers is the wrong way round - there seems to be a fair bit of interest in developing hardware that manages it's own energy consumption without loss, either in additional power to bring it back up to speed or in processing lag, etc. Of course, this doesn't address the poster's immediate concerns to which I have little to add other than it's probably good to cost in heightened risks of hardware failure and therefore the costs of unscheduled downtime.
Excepting google and such, I doubt that the vast majority of servers would have such a geographically balanced workload.
upon the advice of my lawyer, i have no sig at this time
Google likely shunts load to different datacenters based on location.
-mkb
He didn't say website, he said "web servers" which, despite the name "web", could serve an internal web-based service to a large company that only exists in one region of the world.
Its quite likely that, even if your server is serving the public over the internet (which is certainly not the case for all servers), the userbase isn't spread uniformly across all available timezones.
As long as power use is built into the fixed price I pay for the cabinet I rent at the colo, I'll never turn off my servers if I don't need to. Why would I?
Power outages present a very different scenario to the system from powering things down the right way...
On second thought, let's not go to the internet. 'Tis a silly place.
No really. On certain times of the year (ie. not summer), I reduce/eliminate the cooling of the server room AC and redirect the server waste heat to warm the rest of the office. Ambient air from the office space is ducted/filtered in near the floor, and a 300 CFM fan takes in the heat at the ceiling above the server tower. I estimate I capture between 9,000 & 12,000 BTU of heat an hour because of this; greatly reducing the HVAC needs of the building during the night.
This was a large part as to why the EPA gave my company one of their Annual ENERGYSTAR Energy Conservation Awards.
It never made sense to me to run an AC unit when it's snowing outside.
http://www.energystar.gov/index.cfm?c=sb_success.sb_successstories2008_johnsonbraund
I would think that if any servers can be regularly powered off, then they probably fall into one of two categories, they aren't really needed or they are only loaded at certain times. In both cases there's a good reason for consolidation, whether it be physical or virtual. obviously virtual gives the best bang for buck. I run several ESX clusters and despite dept's not trusting virtual servers, they all come around in the end. I think virtuals really are the only way to go to really save money, space, power, and the all important UPS load. Don't forget, the myth about hard disks dying after they have been running for a long time and then allowed to cool after a power failure, well that myth isn't a myth, it happens, and it happens a lot.
I cannot think of situation where powering off a server that is needed provides any benefit whatsoever, you might save a few dollars, but as we all know when you're IT dept struggles to get budget for anything, the risk of failure and the HUGE costs associated with that far outweigh ANY power savings you might achieve.
I don't give a rat's arse if powering off a few minor servers saves $100 a month, when if the disk dies after it cools down, and I then have to go into repair mode to find out what peculiar apps were installed on the server, somehow scrounge another system with no budget, and then rebuild the whole damn thing, only to find out the developers have changed so many configurations it takes weeks or months before everything is really working as it should. Even more joy is that usually occurs at night if power is lost, as we have nothing better to do anyway. NO THANKS!
For companies who have massive budgets for IT, and routinely swap out hard disks, etc, maybe that would work, most companies I know and have worked for over the years though tend to view IT as a parasitic loss centre run by people who spend there days watching the blinkety lights and having fun, "it's just a bunch of servers, how hard could it be" or "how much money could they need, I can go the PC shop and get a whole quad core rig for $600!"
But I will say, nothing gets Capital Exp forms signed faster than a major downtime!
But what happens to all of the servers that fail to start up in time to process payroll? It's late? You pay overtime through the nose for th SysAdmins that have to come in and work 24 hour days to bring the machines online? Seriously, I'm not saying it's a bad idea but I would say that this scenario is probably more like 15 days on 15 days off. You have to build in time on the front end to make sure the machines are up and running in a stable configuration, and probably time on the back end to apply patches and perform metrics on the machines to make sure they are running properly for next month. I'm not sure that this would save anyone any money in the long run because of the load on their staff during spin-up.
Wait, you know of a place where sysadmins are paid overtime? Or even by the hour?
Check out my sysadmin blog!
Must be nice to be able to load balance by datacenter as opposed to physical (or virtual) machine.
Check out my sysadmin blog!
It never makes sense to power down a server that supplies web pages, if you are in e-commerce.
The moment your potential customer sees a 404 page, you've lost him.
Indeed we design all our pages to be displayed in less than 7 seconds, as our research showed anyone typically waiting longer than that for say "search results" would be likely to go elsewhere rather than waiting.