[Sunhelp] Problem with E220 "redundant" power supplies

[Bill Bradford]

For those of you who dont know, E220Rs have two power cords each, for
redundancy - they can run fine w/one.  Anyway, here's a description of
my strange problem.

We have two UPS units in our datacenter right now, call them "A" and "B".
Systems are plugged into both units right now, but tonight, we had to
move everything to "A" because "B" is being shut down (to add more batteries)
this coming Friday.

"no problem" I thought, "since all the 220s have dual power cords, we wont
even have to shut them down - just do the shell game with the power cords
until everything is plugged into UPS-A".

It didnt quite work this way.

Here's what happened.  Say each 220 has a power cord #1 and #2.

1.  All machines have power cords plugged into "first available outlet".

2.  I plug power-strip-1 into a UPS-A outlet.  One by one, I unplug
	Power Cord #1 from each 220 into power-strip-1.

3.  I unplug each 200s Power Cord #2 and let them sit for a minute while
	I untangle everything.  All machines are still up at this 
	point, running off the power strip plugged into UPS-A.

6.  I take all the 220s Power Cord #2s, and plug them into 
	power-strip-2.

7.  I unplug power-strip-2 from UPS-B.  All the E220s die, even tho 
	they had been (and still should have been) getting power 
	from power-strip-1, which was already plugged into UPS-A.

8.  I plug power-strip-2 into UPS-A.  All machines fire back up,
	and appear to come up normally. (whew)

Therefore, it seems that the machines didnt failover between redundant
power supplies/cords properly; if power-strip-1 was bad, they should
have all died when I unplugged the power cord #2s - but they didnt.
They died after I had all the power cord #1s going to UPS-A, all
power cord #2s going to UPS-B, and unplugged power-strip-2 to move
it to UPS-A.

Thoughts?  Suggestions?  Anybody else seen this problem?  I cant
take the boxes back down to "try it again", but I'm getting another
E220 in a couple of days that I'm gonna try this with and see if it
does the same thing.

Bill

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+-------------------\ /-----------------+
| Bill Bradford      |  www.sunhelp.org |
| mrbill at mrbill.net  |   www.decvax.org |
| Austin, Texas USA  |    www.pdp11.org |
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