Re: redundant power supply - moving one cord

[Roberto José Etcheverry Romero <yggdrasil.raiker@xxxxxxxxx>]

There's another important reason not to go around unplugging PSUs.
570's PSU had a fatal design flaw (in my opinion) in that the PSU's fan was
the CPU fan as well. When one fails the other goes to 100% to keep the
CPU's cool. The problem is that those fans get old and might run OK at the
lower speeds but fail at 100% so when one PSU fails... the other one also
fails due to the fan not reaching 100%!
I've replaced a lot of those PSUs both in Power5 and Power6 enclosures.
Haven't seen that design in current machines but as always, when using
multiple PSUs, unplugging one means that instead of sharing the load the
other one has to carry the entire machine.
I've also seen cases where the UPS is NOT sized correctly for the full load
and when one UPS fails (or the mains feed fails, in cases where there's one
UPS and one mains connection), the UPS shutdowns due to overload and down
go the machines...
One of those cases ended up with a Priority 1 call to IBM due to pinned
data in a v9000, so, take care.

Roberto

On Fri, Nov 2, 2018 at 12:59 PM Musselman, Paul <pmusselman@xxxxxxxxxxxxxxxx>
wrote:

> Nor does the better man replace a disk cache battery during the meat of
> the production day.
>
> At least not more than once!
>
> Paul E Musselman
>
> -----Original Message-----
> From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxx> On Behalf Of DrFranken
> Sent: Thursday, November 01, 2018 4:14 PM
> To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
> Subject: Re: redundant power supply - moving one cord
>
> Power7???
>
> Yes this should work but there were some flaky units on Power7 8202-E4Bs
> and E4Cs at one point that did not come back up when connected to the
> new source. This is identified by the green light not going steady.
>
> I have moved Powe5, 6, 7, 8 all in this manner. Never had to move a
> Power9 yet but suspect it will work without issue.
>
> Nonetheless the better man does this NOT during the meat of the
> production day. :-) :-)
>
>          - Larry "DrFranken" Bolhuis
>
> www.Frankeni.com
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