Energy consumption vs % utilization?

Wed Oct 27 09:13:37 UTC 2004

Steven M. Bellovin wrote:
> In message <Pine.WNT.4.61.0410261429110.3340 at 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.

 From running a Colo in a place with ridiculus high electricity engery
costs (Zurich/Switzerland) I can tell you that the energy consuption
of routers/telco (70%) and servers (30%) changes changes significantly
throughout the day.  It pretty much follows the traffic graph.  There
is a solid base load just because the stuff is powered up and from there
it goes up as much as 20-30% depending on the routing/computing load of
the boxes.  To simplify things you can say that per packet you have that
many "mWh" (milli-Watt-hours) per packet switched/routed or http requests
answered over the base load.  I haven't tried to calulate how much energy
routing a packet on a Cisco 12k or Juniper M40 cost though.  Would be
very interesting if someone (student) could do that calculation.

-- 
Andre