saving power in a Dell Poweredge 750.

[Chuck Swiger]

On Jan 10, 2007, at 9:34 AM, George Hartzell wrote:
> I'm setting up a Dell Poweredge 750 1U server.  A friend is loaning me
> space in his rack and since his rack usage is limited by power I'd
> like to be as thrifty as possible.
>
> I hooked my kill-a-watt meter up and ran the machine for a couple of
> days and it uses 88 watts (3.90KWH/44.01H).
>
> Then I kldloaded cpufreq and enabled powerd and it still uses 88 watts
> (8.35KWH/93.47H).
>
> That surprised me a bit, and seems to suggest that it's spending most
> of its energy spinning fans or something.

There isn't going to be nearly as much power savings running powerd  
with a desktop or rackmount equipment than with a laptop-- the latter  
are designed with a low-power mode of operation as a priority due to  
limited battery life.  Also, I think that powerd also doesn't help  
that much compared with the "HLT in the idle task" approach that has  
been used previously, but YMMV.

Also note that most power supplies are rated for around 80 - 90%  
efficiency, which means that a 400W power supply under full design  
load would be be drawing 440 to 480 W.  However, even under zero  
load, they'll still eat a few watts.  Unless you replace the machine  
with something like a VIA EPIA or a Soekris 45xx/48xx using very low  
power components, you're going to have a tough time getting your  
power draw down much lower than the ~90 W.

-- 
-Chuck