Which UPS for two server?

Ronan Mullally ronan at iol.ie
Thu Dec 21 15:04:30 CST 2006

On Thu, 21 Dec 2006, Alessandro FAGLIA wrote:

> > 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!)

Use one UPS and plug the second PSU on each server into the mains supply.
You protect against mains failure with the UPS and UPS failure with the
mains.  If mains fails and the UPS runs low it'll shut down the servers.
If the mains supply returns the UPS won't need to signal for a shutdown.

The only things you're not protecting against is and extended outage or
something that'll take out both the mains *and* the UPS (but that's likely
to be something very nasty indeed).


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