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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?"
Like when someone posts your domain name on slashdot!
You can't take down a server that's already off-line.
you see the Windows logo appear? (sorry, couldn't resist)
Attention all planets of the Solar Federation! We have assumed control! - Neil Peart
The best time to shut down the servers is right before you quit your job. Password-protecting the BIOS first adds value too.
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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I'm glad this was posted to "Ask Slashdot" where your audience is highly seasoned professionals that can give you wise, insightful answers...
In the data center that I manage, I use a few simple rules to determine when I power them down.
1) If the server is on fire
2) If there are no users using the server
or
3) If the power company is saying that I haven't paid my bill and they are sending "Hank" over to cut me off
4) Civil unrest, tornado, earthquake, zombies, etc.
If you virtualized your servers, you could create a managed power-down/power-up scenario. In the morning, your servers would turn on, your virtualized instances would move around (so they have more power for the day's activities), and then at night they'd retreat to a smaller group of servers. The unused servers could shut down for the night. You could even rotate which servers stay on overnight keeping the virtual servers running to spread the wear around if there is some.
Seriously, this analogy makes sense. When a car is cruising on the high way it's able to maintain speed using 4/8 cylinders. Servers could be cycled in a similar fashion. Do you really need 20 web servers running at 3 am on a Sunday?
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.
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.
Full disclosure, I work for Citrix. Check out XenServer, which can remotely provision server workloads to virtual and bare metal machines - based on load, you can remotely power up resources as needed. I have seen the future, and it is awesome. And green.
Atari, System V, C64, Amiga, College Unix (?, I wasn't like root or nothin'), Mac, WinNinetySighs, NT, Novell, Win2K, So
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.
The problem is the PSU, which fails most often during power-up. Leaving the servers always on has the advantage of avoiding that particular failure mode. Also, other components in the server are prone to failure during power-up, way more often than at steady state. So, powering up your computers is overall a risky moment.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
Analogy (this time, light bulbs).
- Light bulbs fail just as you turn them on. Or off.
- They hardly ever fail whilst switched on.
I think servers are the same. You're in trouble if a server you've had switched on for two years and forgotten about loses power and doesn't come back up. If it'd been switched off every weekend it would have failed earlier -- but probably at a more convenient time.
(My datacenter charges about a buck a VA)
A watt?
chris@xanadu:~$ whatis /.
/.: nothing appropriate.