rack power question

Thu Apr 3 19:50:25 UTC 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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