Which UPS for two server?
a.faglia at farmol.it
Thu Dec 21 06:52:33 CST 2006
Robert D. Holtz - Lists wrote:
>> 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
> 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.
So the total absorbed power I read in data sheets refers to both
suppliers working? Or should I double the number?
>> 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 UPS.
Nice tip, but: if I do so, how am I going to drive the shut-down of
servers if batteries are runnign out of power? How can I manage this
aspect? In the worst case, the second UPS may fail, the first supplier
of a server may fail, and the server finds itself without power... (this
can be the n-th Murphy's law!)
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