Which UPS for two server?

Stephan Wonczak a0033 at rrz.uni-koeln.de
Thu Dec 21 06:15:44 CST 2006

On Thu, 21 Dec 2006, Alessandro FAGLIA wrote:

> Dear list,
> I am going to buy two new PE servers, the 1950 and 2950.
> Both of them will be provided with redundant power supplier.
> The PE 1950 will have two 73GB SAS disks (RAID1) while the PE 2950 will
> have three 73GB SAS disks (RAID5).
> From data sheets I see that PE 1950 requires 670W while PE 2950 needs
> 750W. Total: 1420 W.
> My concern is about redundant power suppliers. I think that during
> normal operations, only one of them is actually working, and in case the
> first breaks, the second takes over the faulty one and stars working.
> What is going to happen in the switching moment? Will I have a current
> spike?

   You won't ... The power supplies of the 1950/2950 are active/active, not 
active/passive. So no switching going on.
   Also, as has been noted otherwise, the ratings of the PSUs are maximum 
values. Normal load usually is a lot less, maybe half of the maximum as a 
rule of thumb.

 	Dipl. Chem. Dr. Stephan Wonczak

         Zentrum fuer Angewandte Informatik (ZAIK)
         Regionales Rechenzentrum der Universitaet zu Koeln (RRZK)
         Universitaet zu Koeln, Robert-Koch-Strasse 10, 50931 Koeln
         Tel: ++49/(0)221/478-5577, Fax: ++49/(0)221/478-5590

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