Drives spinning are at idle. Drives seeking are active. Assuming these are Seagate Cheetah 15K RPM drives, the power draw differences can be found at
http://www.seagate.com/docs/pdf/datasheet/disc/ds_cheetah_15k_5.pdf. Basically about 5 watts difference per drive, the difference being head seek activity.
The power draw for memory draw won't really change.
For the CPU however, well, just read some of the power management articles about the POWER CPU family or even the Intel & AMD offerings will have you realize that idle and active draw on modern CPUs varies a lot. Without looking it up I'd guess 35-50 watts per core difference between idle & 100% active.
But it doesn't end there. If the CPU is active, the cooling fans are likely spinning faster to increase air flow/cooling capacity. Most modern servers have thermally activated fans; the higher the temperature (caused by system activity) the faster the fan speed. The faster the fan speed the more power the fan(s) draw(s). So add a few watts for higher fan activity. Ditto the higher the ambient temp in the room the more air the fans will have to move.
And the more power is being drawn the more the PSU's fans will have to spin, drawing even more. Although this is probably partially balanced by the PSU becoming more efficient as power draw rises.
I would say two things:
1. If you want to actually measure it, arrange to power down the system so you can use one of these:
http://www.p3international.com/products/special/P4400/P4400-CE.html (or one of their other models). I use the EZ model (
http://www.p3international.com/products/p4460.html) to monitor PC power consumption. They also have a power strip model.
2. Read the physical planning reference or look at the size of the PSUs and make sure you size your UPS and power circuits to accommodate the maximum draw.
--
John A. Jones, CISSP
Sr. Analyst, Global Information Security
Jones Lang LaSalle, Inc.
Voice: +1.630-455.2787
FAX: +1.312.601.1782
Email: john.jones@xxxxxxxxxx
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of ChadB@xxxxxxxxxxxxxxxxxxxx
Sent: Monday, December 15, 2008 3:31 PM
To: midrange-l@xxxxxxxxxxxx
Subject: System power question
OK... this is a strange question...
Picture an i5 system (a 3800 cpw 525) that is powered on and humming away
as it processes work to support Mimix replication, a Domino server, and a
WAS/HTTP server.
Now picture that same i5 system (a 3800cpw 525) that is powered on and
sitting in restricted state.
Now here's the question... are they consuming approximately the same amount
of electrical power from the circuit (conditioned by the UPS, of course)?
If there is a difference in the electrical power being drawn, is it a
significant difference? I'm looking to get a handle on this question... I
can make a guess, but i'd like to hear from someone who is certain of the
answer!
--
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