Which UPS for two server?

PMilanese at nypl.org PMilanese at nypl.org
Thu Dec 21 08:47:13 CST 2006

>> 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?

>The power supplies run in active/active mode, i.e., they're both feeding
>power to the system.  There is no switch period.  On failure more current
>starts flowing through the one that's still okay.

>> My question is: which is the best (in terms of available power)
>> rack-mounting UPS that I can buy to serve these two babies?
>> If the total power is 1420W, I could go for the APC Smart-UPS 3000i,
>> 2700 watt (probably the APC Smart-UPS 2200i, 1600 watt is enough, but
>> the load will be tight to 100%). What about the current spike I
>> mentioned before?

>Buy two APC rack mount units.  Model is your preference of features.  Take
>one power supply from each server and feed it from the first UPS and take
>the second power supply from each server and feed them from the second

Agreed on all points. You get 2 power sources so that failure is minimized.
Throwing it all on one UPS would negatively impact the purpose. I've had
more UPSs fail than power supplies.

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