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  3. May 2006

RE: Redundant Power


I was surprised you even thought about that one    ;)

                                                                       
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             PM                                                        
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                                       RE: Redundant Power             
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Ok, you talked me out of it.

Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





"Jones, John \(US\)" <John.Jones@xxxxxxxxxx>
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05/30/2006 01:47 PM
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Subject
RE: Redundant Power






If that wall plug is serviced by the same electric utility that services
the UPS, then the UPS still needs to be sized to run the entire load or
all is moot in an electrical outage.  And power outages (blackouts,
brownouts, blips, rolling blackouts, etc.) are in general going to be
more common than failed PDUs, line cords, or iSeries PSUs.

Also, I'd wonder about surges & sags and other variances in power
quality if the wall power wasn't filtered somehow.  I don't know that
PDUs really do any filtering as they can reasonably expect clean power.

And if lightning strikes the power grid, the UPS, which would otherwise
control the spike and protect the computers, might get reverse-fried by
a spike coming in through the wall plug and routing through (while
frying...) the iSeries and back to the UPS.  Some years ago at a
different employer, we had lightning strike a datacomm line.  It fried
our leased line modem, went through it to fry our 5294 twinax
controller, and went down the twinax lines to fry about 6 terminals.

UPSes are relatively cheap insurance.

John A. Jones, CISSP
Americas Information Security Officer
Jones Lang LaSalle, Inc.
V: +1-630-455-2787 F: +1-312-601-1782
john.jones@xxxxxxxxxx

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Tuesday, May 30, 2006 12:26 PM
To: Midrange Systems Technical Discussion
Subject: Re: Redundant Power

I don't know.  We have had some times where the UPS went down.  If one
chooses not to spring for a second ups what do others think about
splitting between the UPS and a wall plug?

Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





ChadB@xxxxxxxxxxxxxxxxxxxx
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05/30/2006 01:18 PM
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Subject
Re: Redundant Power







Makes sense.  Our setup would offer redundancy only to the point of the
UPS.  We would have dual power supplies, dual line cords, dual PDUs in
the
rack, but both PDUs would plug into the same UPS.  Not an ideal level of
protection, but it would protect from some common things like failed
power
supplies, and damaged (or yanked!) cables.

Splitting the 2 supplies between a UPS and a wall plug sounds like
trouble
all around!


             Larry Bolhuis
             <lbolhuis@arbsol.
             com>
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             05/30/2006 12:38
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             PM                        Re: Redundant Power


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Pretty much the same thing. In order to have two cords you need two
supplies.  In order for it to be effective at all they must be
redundant. For example if you did this with a i270 or an i810 that had
two supplies you would be setting your self up for a failure of the UPS
*OR* the wall plug failing to drop the system because those power
supplies are not redundant.

If the supplies are billed as redundant that Must mean that each can do
all the work if required and without any action by the user. Either of
them can suddenly be the only one working but the system stays up.

In the case described here the supplies each carry roughly 50% of the
load so the outlet and the UPS each get half. If the outlet goes dark
then only the UPS remains to supply both it's current 50% plus the
outlet's 50%. When there isn't that much headroom on the UPS then the
UPS shuts off in self protection.

 - Larry

ChadB@xxxxxxxxxxxxxxxxxxxx wrote:

You're talking about splitting the cords between utility and UPS, and

not

about the reduntant power supply, right?



*WARNING* *WARNING* *WARNING*

In this configuration you *MUST* be certain that the UPS is never over
50% load! If it's at even 51% when the power fails and the UPS must
carry all of the load instead of only half it caries now it will drop
like a stone leaving you completely unprotected and of course

unpowered

as well!!.

The only way to test this for sure is to unplug all the power supplies
that go into the wall and see if the UPS can stand it!

 - Larry

Chris Bipes wrote:


--
Larry Bolhuis                   IBM eServer Certified Systems Expert:
Vice President                    iSeries Technical Solutions V5R3
Arbor Solutions, Inc.             iSeries LPAR Technical Solutions V5R3
1345 Monroe NW Suite 259          iSeries Linux Technical Solutions V5R3
Grand Rapids, MI 49505            iSeries Windows Integration Technical
Solutions V5R3
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(616) 451-2500                    iSeries System Administrator for
OS/400 V5R3
(616) 451-2571 - Fax              AS/400 RPG IV Developer
(616) 260-4746 - Cell             iSeries System Command Operations V5R2

  If you can read this, thank a teacher....and since it's in English,
thank a soldier.


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