rack power question

Jon Lewis jlewis at lewis.org
Sun Mar 23 17:33:25 UTC 2008


On Sun, 23 Mar 2008, Ray Burkholder wrote:

> My desktop has a 680 Watt power supply, but according to a meter I once
> connected, it is only running at 350 to 400 Watts.  So if a server has a
> 980W power supply, does the rack power need to be designed to handle
> multiples of such a beast, even though the server may not come close
> (because it may not be fully loaded with drives or whatever)?  Wouldn't it
> be better to do actual measurements to see the real draw might be?

This depends on who's providing the power.  If it's your power and your 
servers, you can "know" that your 980W supplies are really only using 
600W, be happy, and plan accordingly if you upgrade later.

If you're providing the power, but it's someone else's gear, you better 
have good communication when it comes to power requirements/utilization, 
because what happens when they install more drives/processors next month, 
and those systems that were using 600W suddenly are using 800W each?

When providing/planning UPS power, if you sell a 120V 20A circuit, do you 
budget 120V 20A of UPS power for that customer, or 16A (80%), or even 
slightly more than 20A (figuring worst case, they're going to overload 
their circuit at some point) when deciding how full that UPS is?

----------------------------------------------------------------------
  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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