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Re: rack power question

  • From: Derek J. Balling
  • Date: Thu Apr 03 15:54:50 2008
Sorry to resurrect a slightly old thread, but I did want to touch on something I noticed while catching up.

On Mar 25, 2008, at 6:12 PM, Michael Brown wrote:
Naturally, that's redundant, so theoretical maximum usage per rack is
half that, 23200W. Plus, the blades available today don't draw enough to
fully load those power supplies. In the config I'm looking at now, a
single blade (2x Quad-core 2GHz Intel, 4GB memory, no hard drives) draws
232W max, 160W lightly loaded. Let's pull a number of 195W out of the
air to use.

Don't be so sure that's actually redundant. At $JOB->{prev}, we had a fully populated IBM H chassis that had fully populated power supplies where the chassis spent its entire life in an alarm state that there was "insufficient power redundancy" ... the draw of the loaded chassis (14 blades, 2 mgmt cards, 2 switches, 2 FC switches) was more than a single "side" of power could handle. The chassis notified us that if it lost a side of power it was going to throttle back the CPUs to account for the loss.

So your theoretical maximum draw is NOT "1/2 the total"... in a nicely populated chassis it will draw more than 1/2 the total and complain the whole time about it.

Cheers,
D

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