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Linux Power Management

August 8th, 2006

Save energy by reducing the processor speed of your computers when not in use.

I've tried lots of different power management techniques with linux. I was successful in getting hibernate to work with suspend2 sources on my Toshiba laptop (howto to come) and finally I got Power Now to work!

For my system, I loaded the following kernel modules:

  • powernow_k8
  • thermal
  • cpufreq_conservative
  • processor

Though I guess I don't need it, I could not modprobe acpi-cpufreq:

FATAL: Error inserting acpi_cpufreq (/lib/modules/2.6.17.1/kernel/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.ko): Device or resource busy

Unfortunately, the lower processor setting only saves a few watts. Better than nothing. Especially for a machine that is on 24/7/365!


I am also trying to get my UPS into the loop. I have an APC Back UPS 500, connected via USB 2 Ethernet, so I'm going to try apcupsd. I did get apcupsd to install and run. I'm very impressed so far!

http://www.docunext.com/2006/08/apcupsd-notes/


This machine uses a software raid, and the performance is amazing. However, since this machine is on 24/7/365, I'd like to save a little juice at night. I was weary about using hdparm for sata drives configured in a raid, but it seems kosher. I DO NOT ADVISE YOU TO TRY IT! These are just my thoughts.

http://freshmeat.net/projects/hdparm/

http://kangry.com/topics/viewcomment.php?index=227

Using the trusty Kill-A-Watt meter, I was able to check the difference between standby disks and active disks, and it is over 20 watts. I'm definitely going to set that up. Right now I can't because we run Asterisk and Nagios on the same server, which writes to the drive fairly often. I did set the commit time for the ext3 filesystem to 7200 (two hours), and am also using laptop-mode-tools. I think this is doable.

Many sites have explained that constantly spinning down and spinning up your drives causes them to fail faster. I agree with this statement, but seeing that heat can also hurt computer components, spinning down the drives once a day should be fine. I would shut down the computer alltogether, but that would then prevent me from being able to access the server if I need to.


These websites were very helpful for ACPI:

http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/

http://forums.gentoo.org/viewtopic.php?p=1970584

http://www.tldp.org/HOWTO/html_single/ACPI-HOWTO/

And this one for apcupsd:

http://www.apcupsd.org/manual/

¥

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