On 2011-10-19 13.26, Raimo Niskanen wrote:
> Also, a smart UPS can be told not to apply power to the machine
> until it has reached a sufficient (settable) charge level after
> the power comes back.
>
> If the power comes back and disappears again, which is not too uncommon
> when all starting devices on the power network causes overload;
> without sufficient charge level the machine may not have time to even
> start properly before the battery is completely drained, and thus
> fails to detect UPS on battery and do a shutdown.
On the other hand, a smart enough UPS can be told all that (except exactly
when to kill power to the servers) regardless of it having to have "smart"
communications with a host server.
Also, I don't think the most common use case for a UPS is a 1:1 relation
between UPSes and servers. I have several servers hanging off of each of
mine, and they certainly don't (can't) all communicate with the UPS.
Not that it isn't neat to be able to talk to your UPS, I'm just saying the
most important needs - to spare servers the shock of sudden death - can be
accomodated without. :-)
/B
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