Re: Energy consumption vs % utilization?

["Steven M. Bellovin" <smb () research att com>]

In message <Pine.WNT.4.61.0410261429110.3340 () vanadium hq nac net>, Alex Rubenst
ein writes:
> Hello,
>
> I've done quite a bit of studyin power usage and such in datacenters over 
> the last year or so.
>
> > I'm looking for information on energy consumption vs percent utilization. In
>
> > other words if your datacenter consumes 720 MWh per month, yet on average 
> > your servers are 98% underutilized, you are wasting a lot of energy (a hot 
> > topic these days). Does anyone here have any real data on this?
>
> I've never done a study on power used vs. CPU utilization, but my guess is 
> that the heat generated from a PC remains fairly constant -- in the grand 
> scheme of things -- no matter what your utilization is.

I doubt that very much, or we wouldn't have variable speed fans.  I've 
monitored CPU temperature when doing compilations; it goes up 
significantly.  That suggests that the CPU is drawing more power at 
such times.

Of course, there's another implication -- if the CPU isn't using the 
power, the draw from the power line is less, which means that much less 
electricity is being used.

                --Steve Bellovin, http://www.research.att.com/~smb