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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 Sent by: midrange-l-bounces@xxxxxxxxxxxx 05/30/2006 01:18 PM Please respond to Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx> To Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx> cc 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> To Sent by: Midrange Systems Technical midrange-l-bounce Discussion s@xxxxxxxxxxxx <midrange-l@xxxxxxxxxxxx> cc 05/30/2006 12:38 Subject PM Re: Redundant Power Please respond to Midrange Systems Technical Discussion <midrange-l@midra nge.com> 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:
midrange.com
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