That's excellent information. I was surpised by how close to the
documented power use my number were. Knowing that even high disk use
adds little power usage is important to though of us fighting the
power/cooling wars.
Mike
Bruce Allen wrote:
I have spun up Sun x4100 dual core, dual processor to 100% processor
usage and normal HD writes and measured the actually powerusage at 267
watts. Obviously higher than normal HD usage (such as swapping) would
drive the number up,
Even heavy disk thrashing would only drive the number up by a few watts.
Typical SATA disk are around 6 or 8W normal power use [except on power
up, when spinning up the platters can increase power use by 15W for one
or two seconds]. Once the disk is spun up, seeking the heads back and
forth as fast as possible while reading and writing only increases the
power use by a few watts.
Here is a specific example for illustration: Hitachi Deskstar T7K250
250GB, reference OEM manual, Version 1.8, 12 September 2006,
http://www.hitachigst.com/tech/techlib.nsf/products/Deskstar_T7K250 .
Note: I choose this disk NOT as an endorsement of any kind but because
Hitachi/IBM have detailed OEM manuals on their web site, and because it
is a typical high-sales-volume inexpensive dual platter 7200 rpm SATA disk.
Citing from section 7.4 of the OEM manual:
Idle average: 6.2W
Random RW average: 10.5W
So heavy disk loading would drive up the power consumption by 4.3W,
which is less than 2% of the total power use of the node.
Most of the power in typical cluster machines is consumed by the CPU(s),
the chipset(s), inefficiency in the power supply, and the memory. On
thing that surprised me a bit the last time I looked at this a year ago
was that the power use of typical memory sticks is quite high, often
more than 10W. In fact if you look at system with well-designed cooling,
you'll see that the fans are designed to blow a lot of air over the
memory area.
Cheers,
Bruce
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