[Beowulf] power usage, Intel 5160 vs. AMD 2216

[Bruce Allen]

> 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