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

[jmmckee <jmmckee@xxxxxxxxxxxxxx>]

In 13 years at my present employer, we did have a power supply failure.  It was a 620 with one supply.  The CE had not seen one fail.  A replacement took almost ten hours to arrive, and then there was the rebuilding of access paths. I do not recall if dual power supplies was an option on that 620, or whether somebody thought the second supply was too expensive.  The real expense of a downed system for nearly 24 hours had to be more than a second supply.  Even replacing the thing on the 620 was time consuming.  Back in the 90s, I recall a sales pitch about EMC disk modules.  They had THREE supplies.  Two were required to run the unit.  

John McKee


-----Original message-----
From: "James H. H. Lampert" jamesl@xxxxxxxxxxxxxxxxx
Date: Mon, 02 Aug 2010 18:56:00 -0500
To: Midrange Systems Technical Discussion midrange-l@xxxxxxxxxxxx
Subject: Re: Monitoring for power outages on a dual-powered system

> Simon Coulter wrote:
>
> > Of course there is. Redundant power supply units are to protect  
> > against failure of one power supply unit.
>
> 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).
>
> --
> JHHL
> -- 
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