This issue has the potential to cause additional mechanical wear and tear on rotational hard drives by causing them to spin up and down more frequently than in previous Ubuntu releases. While the intent of a development change in the precise cycle was to allow drives to spin down sooner and stay spun down, in practice users report their drives spin back up quickly. Until this is resolved, an aggressive spin-down policy is dangerous for hardware and inappropriate.
1. On a laptop with a rotational hard drive, unplug main power and run on battery.
2. Run sudo smartctl -a /dev/sda|grep Load_Cycle_Count repeatedly, to observe that the count increases once every few seconds.
3. Install hdparm from precise-proposed.
4. Plug the laptop back into main power, then unplug it again.
5. Run the command from step 2 again. Observe that the count is no longer increasing or is increasing much more slowly. (Note that the precise behavior will vary from hard drive to hard drive, and on some systems there will be no difference visible at all.)
For some users the current setting does not meaningfully increase wear and tear on their drives, but changing it will increase power consumption. This seems to be a necessary evil since there's no single power saving setting that works well for all drives.
After update from Oneiric to Precise Beta 1, kernel 3.2.0-18-generic, I notice that, when on battery, my Dell XPS M1330 laptop has its HD spin down, then restart, very, very, very often, which means several times per minute.
At this pace the HD won't live long, and this reminds to me a problem we had few years ago with "disk killers" linuxes that were unloading/reloading the HD heads much too often, killing disks in a couple of months.
So I prefer to ring the alarm bell early...
Upgrading from Oneiric to Precise I didn't change any power management parameter, but it definitely didn't do this before (and still doesn't do this on other distros I have on multiboot, so that's no hardware issue, only Precise does that on my machine...)
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-18-generic 3.2.0-18.28
ProcVersionSignature: Ubuntu 3.2.0-18.28-generic 3.2.9
Uname: Linux 3.2.0-18-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
USER PID ACCESS COMMAND
/dev/snd/controlC0: michel 3044 F.... pulseaudio
(2402 - 2482 @ 40), (N/A, 20)
(5170 - 5250 @ 40), (N/A, 20)
(5250 - 5330 @ 40), (N/A, 20), DFS
(5490 - 5710 @ 40), (N/A, 27), DFS
Card hw:0 'Intel'/'HDA Intel at 0xf6dfc000 irq 46'
Mixer name : 'Silicon Image SiI1392 HDMI'
Components : 'HDA:83847616,1028020a,00100201 HDA:10951392,1028020a,00100000'
Controls : 33
Simple ctrls : 19
Date: Sun Mar 11 22:25:00 2012
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
MachineType: Dell Inc. XPS M1330
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.2.0-18-generic root=/dev/mapper/VG1-UBUNTU ro clocksource=hpet quiet splash vt.handoff=7
UpgradeStatus: Upgraded to precise on 2012-03-10 (1 days ago)
dmi.bios.vendor: Dell Inc.
dmi.board.vendor: Dell Inc.
dmi.chassis.vendor: Dell Inc.
dmi.product.name: XPS M1330
dmi.sys.vendor: Dell Inc.