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04 January 2013

Attaboy X220 with atactl!

Spin that disk down

My Lenovo Thinkpad X220 has two disks, the Hitachi 320Gig drive it came with and a 64Gig Kingston mSATA SSD that I fit in there myself. The system (OpenBSD) and most of my home dir are on the SSD, which makes for a more responsive system. On the other there is a large partition that I mount into my home dir for the bigger digital cruft that always assembles over time. So in theory I could unmount the spinning disk and get more quiet and less energy consumption, but that didn't happen automatically. Yesterday though, my friend Rodolfo told me about atactl(8). Now that is a fun tool...

What I can do with atactl is first of all to see all kind of techy info about my drive like SMART status and power management state. I don't know why, but the state is always reported as "standby". More important though: The command sudo atactl sd0 sleep will spin down the drive and put it into "sleep mode". You can hear the drive spinning down and then emitting a little "beep", just like it does when powering down the laptop.

I guess this will save me some battery time. A first glance on systat sensors seems to indicate something like 0.5 Watt less draw on the battery, but frankly I have no clue how to interprete these values, they seem to be a bit all over the place. The next time that I will work for a long stretch from the battery I'll compare the time I get and see if there is a meaningful difference.

Spinning down that disk to "sleep" mode also reduces a lot of noise from the laptop. Now there is something that I don't need to measure, especially in a quiet environment. The "wirr" of the disk is gone, while the much lower sound of the fan is still heard.

Once the laptop was in suspend mode and waking it up again, the disk is again in spinning mode. Another way to spin it back up is to issue any other atactl command, even a simple sudo atactl sd0 to read out the settings. Spinning it up takes some time - so long, the first time I thought it wouldn't come back. I haven't tried directly mounting a partition from that drive while it's "sleeping", but I guess the OS will remember to spin it up again, and if not, it's easy to wake it up with atactl.

Update: One downside I just noticed: When the disk is in sleep mode, suspending the laptop takes a long time. Quite obviously the attempt to set the disk in sleep mode first wakes it up again: The disk light is on and the time to wait is about the same as when spinning up the disk manually with atactl.

Posted by betabug at 17:24 | Comments (0) | Trackbacks (0)
ch athens
Life in Athens (Greece) for a foreigner from the other side of the mountains. And with an interest in digital life and the feeling of change in a big city. Multilingual English - German - Greek.
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