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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?"
There are a number of tools and products out there to assist this.
Consider a large (65k+ employees) company that has a several hundred server implementation that they use to process payroll every two weeks. They use a management tool to power them up on Friday, process payroll over the weekend, and shut them down on Monday. The power and cooling cost impact of these several hundred servers *not* running most of the month (6 or so days a month instead of 31) is huge.
Another (and also in use by the same company) strategy is to virtualize the OS instances, spin those up and down as necessary, and then use something like VMWare's VMotion to maximize usage of the physical boxes - and again use another tool to power down unneeded compute capacity.
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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.
...and again use another tool to power down unneeded compute capacity.
And that other tool is ... VMware! DPM (distributed power management) is built right in, and does exactly what you describe.
http://www.vmware.com/products/vi/vc/drs.html (scroll to the bottom)
Welcome to the virtual world...
Yup, the game is officially changed.
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Actually, the other tool in this case is Cisco's VFrame Data Center. The problem with DPM (and other VMware tools) is that they won't let you move a physical box between ESX clusters. If you have multiple ESX clusters, the physical machine stays with it - powered up or not. With VFrame, the system can be powered down, removed from the cluster, and added to another if/when necessary... including any necessary network configuration (VLAN memberships, etc) and SAN configuration (zoning changes, LUN masking).
Not that I'm complaining about VMWare's solution to this problem - they're actually quite complimentary.
-- "Other than that, how was the play Mrs. Lincoln?"