Re: Monitoring for power outages on a dual-powered system

[Evan Harris <auctionitis@xxxxxxxxx>]

Hi James

Well if nothing else having dual power supplies does prevent a
situation where a power cable is inadvertently pulled out.

It also simplifies maintenance when you need to down a UPS for
servicing or to move it, or when want to switch off a circuit for
electrical work.

Regards
Evan Harris

On Tue, Aug 3, 2010 at 11:56 AM, James H. H. Lampert
<jamesl@xxxxxxxxxxxxxxxxx> wrote:
> This is POSITIVELY THE LAST THING I WILL SAY ON THIS:
>
> 1. In over sixteen years of experience with IBM midrange systems, I have
> never, once, seen an internal power supply unit fail. On the other hand,
> A. I have seen line power fail multiple times
> B. I have seen UPSs from two different manufacturers fail with
> absolutely no advance warning whatsoever
> C. I have seen UPSs send "On Battery Power - battery nearly dead"
> messages through the monitoring cables, during self-tests, on more than
> one occasion, when there wasn't a damned thing wrong with the line power.
>
> 2. If, as you say, multiple redundant power supplies were not intended
> to be plugged into separate power sources to guard against one of the
> sources going down, THERE WOULD BE NO REASON FOR TWO SEPARATE AC CORDS.
>
> The question is about monitoring for one or the other power source
> cutting out at a time when nobody is here to notice, NOT monitoring the
> UPS itself (which we do NOT do, PRECISELY because item 1C has occurred
> on multiple occasions).