For reasons beyond the scope of this entry, today I was curious how much power our servers were using. If you have sufficiently fancy PDUs , I think you can get per-outlet measurements that are trustworthy, but we don't have such PDUs. Instead, the best I can do is look at the information that some of our servers report through IPMI . I'm not sure how accurate the IPMI information is, but at least some of the numbers seem plausible, so I'll assume that it's not massively off. The results surprise me with how low they were.
Most of our servers are basic 1U servers with a pair of SATA SSDs. They're typically not very active, and the not particularly active servers that report IPMI power usage are reporting anything from 22 watts to 26 watts right now. A few servers also have a pair of HDDs, and one has four SSDs and is typically active; all of them report 44 watts right now. Our NFS fileservers currently have 24 SSDs in each and are reporting a range of power usage from 47 watts to 62 watts. One interesting case is our perimeter firewall, where we have the active server and an identical running hot spare, both 1U servers. The active server is at 52 watts (and handling about 40 Mbytes/sec of network traffic); the hot spare is idle at 26 watts.
We have a few compute servers that report power information through their IPMI, and the ones that are currently active are reporting the highest power usage. However, even this isn't spectacularly high. The most power hungry machine is a GPU SLURM node , where its IPMI is reporting 330 watts of total power while its GPU is claiming about 166 watts of power draw (its CPU is busy too).
Some of our servers don't report power usage in their IPMI sensor data but will report it through the web interface of their BMCs . I checked two of them, both powerful 1U servers that are essentially identical to each other. The one that is our primary login server is reporting an average of 149 watts and a peak of 195 watts over the past hour. The SLURM compute node, which is currently in active use, averaged 501 watts in the past hour with a peak slightly higher (when not in use it appears to idle around 107 watts).
One of the reason these numbers surprise me is that many of the idle numbers are lower than my desktops . I have a mental image of servers as not being particularly low power or power efficient, just as they're not particularly quiet, but that seems to be wrong. I suppose it's not too odd that people making 1U servers care about power usage and power density, since that's definitely a concern in general in data centers, it just hadn't really occurred to me before.
(Our own use of 1U servers is not particularly constrained by power and cooling.)