Date: Wed, 10 Jan 2007 14:26:17 -0800 From: Chuck Swiger <cswiger@mac.com> To: hartzell@alerce.com Cc: freebsd-stable@freebsd.org Subject: Re: saving power in a Dell Poweredge 750. Message-ID: <D532417C-D3A3-4CC3-BB0A-9C00836F45C0@mac.com> In-Reply-To: <17829.9117.888327.881204@rosebud.alerce.com> References: <17829.9117.888327.881204@rosebud.alerce.com>
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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
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