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Old 02-17-2009, 09:26 PM
vhickman vhickman is offline
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Question Best Practices for Distributing Power Load Across Redundant PDUs

All -

Looking for some recommendations or best practices for calculating power load and how to properly distrubute across redundant pdu's. I'm a newbie so any help would be greatly appreciated.

Thanks
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Old 02-17-2009, 11:25 PM
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KenB KenB is offline
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Hi and welcome to the forums.

Not to be obvious, but actual power load can be measured easily at several points in the distribution system, depending on your interest. And, the best way to balance loads with redundant PDUs is to split the load between them, making sure that neither circuit is loaded to more than 50% of capacity.

Can you elaborate on what you mean? Is this a homework assignment, or are you involved with an actual data center?


Ken
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Old 02-18-2009, 03:47 AM
vhickman vhickman is offline
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Thanks for the reply KenB and the welcome to the forum.

Yes, It's an actual data center assignment, I'm new to this portion of it. I've split up my equiptment across the pdu's for redundancy, but wasn't sure how to properly calculate the power load from each device.

I guess what I'm really looking for the is the correct calculation for determining power load for each device or rack. From their I should be able to accuratley track the amount of power load for each pdu after I've applied the power draw from it.

Last edited by vhickman; 02-18-2009 at 03:58 AM.
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Old 02-18-2009, 01:18 PM
Schumie Schumie is offline
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You'll want to take reading on your equipment.

Depending on the granularity of what you're looking for... if you have decent PDU's then they might have this functionality for a total built in.

Your DC provide may also be monitoring at the breakers and be able to give you an accurate reading as well.
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Old 02-18-2009, 01:52 PM
dcrelocation dcrelocation is offline
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Power load distribution is based on multiple factors. with the following being the two main factor.

1 is actual power load(draw)
2. tiers of availability - if you have a server with 2 power supply needs to be split across 2 different power sources
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Old 02-18-2009, 07:29 PM
vhickman vhickman is offline
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Hey Guys -

Thanks for the replies. We currently don't have pdu's that monitor power draw, it's a brand new facility and I was trying to make sure the load was spread out evenly using a manual process.

I'm splitting my dual power supplies across both pdus for redundancy, and need to know what the power load (draw) is. I know their is a formula for calcualting what the draw would be, but can't seem to find out.
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Old 02-18-2009, 09:33 PM
whitey whitey is offline
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Most devices have power utilizations specs published by the manufacturer. If I am ball parking I use the following formula's:

(PSU Watts) * .80 = Peak Power Utilization in Watts
(PSU Watts) * .40 = Peak Power Utilization in Watts

Please note these are formulas to find ball park consumption of a device.
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Old 02-23-2009, 02:40 PM
vhickman vhickman is offline
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Thanks Whitey (no pun intended).
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Old 02-24-2009, 02:08 PM
cernst cernst is offline
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I've found the specs posted by the manufacturer to be if you run the equipment at 100% all the time. I very rarely see that.

If you want accurate information and your strips are not metered and your breakers are not metered...I think your best bet would to buy your electrician a case of tastey beverage and ask him to put an amp-clamp on the lines in the breaker box (that's what I generally call a PDU...). For sure, that is the best way to figure out power draw.

I recommend getting one power strip that is metered in a lab setting and running various servers on it to see what the individual load is. Or you could make it part of the installation process to put it on the metered strip to determine expected load before going into production.

Edit:
Think of the cost justification for metered power strips. How much of your time and other's time are you going to chew up to determine this information?
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Old 02-27-2009, 02:11 PM
vhickman vhickman is offline
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Thanks Cernst.
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