Re: UPS trouble again. Mainly just venting, but responses are welcome.

What Lukas said. Redundant PSUs. Each on a separate circuit connected to
separate UPSes. Ideally the UPSes will be in different rooms (ours are on
different floors) or at least not adjacent. For our main system it's easy;
the rack has PDUs on both sides so the redundant PSUs have a power cable
going to the left and another going to the right. Using different brands of
UPS isn't a bad idea but is entirely optional. IIRC we're using large APC
units. Some go a step further and say separate generators and even separate
building power feeds. We don't have generators but do have separate
building feeds. In the extreme the separate feeds are from separate
utilities.

Sound like overkill? How much productivity and/or revenue has been caused
by those outages?

A more trimmed down approach would say to have a UPS supporting just one
side of the redundant power feed and leave the other on straight utility
power. In an outage you're relying on that single UPS but it's a risk some
may be willing to take.

We did not put redundant PSUs in the HMC but did for the tape library. If
the HMC goes down hard, it shouldn't be too much of an issue to move the
power cable to the other side & boot it. And if the HD crashes because of
the power outage, we do have a redundant HMC in another data center.

Also, don't forget to either size the UPS and/or generator to include the
HVAC capacity or count on using the UPS just long enough to perform an
orderly shutdown.

On Thu, Mar 5, 2009 at 1:28 PM, Lukas Beeler
<lukas.beeler@xxxxxxxxxxxxxxxx>wrote:

On Thu, Mar 5, 2009 at 19:20, James Lampert <jamesl@xxxxxxxxxxxxxxxxx>
wrote:

The boss is again losing confidence in the whole UPS concept (not
surprising, since our UPSs have, over the past decade, collectively
caused more crashes than they've prevented)

Perfectly normal if you have a reasonably stable power grid.

We recommend our customers to use redundant power supplies in all
servers, and connect each of the power supplies to a different UPS.
Oh, and make sure that those UPSs never run above 35-40% load, as in
the case of an UPS failure the load on it will double.

We've had our up-and-downs with the Powerware UPSs (several
replacement at customers), but in general they've worked without any
major issues such as those described by you.

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