Andrea wrote:
> Hi all,
> 
> I'm writing to report that I have detected the "unload cycle bug" while 
> running SL5.1 on my laptop. This "bug" has received some attention 
> months ago when it was found in Ubuntu¹ and consequently featured on 
> Slashdot².
> 
> 
> ----- SUMMARY -----
> 
> Some hard disk manufacturers ship their drives - especially laptop 
> drives - preset with some aggressive power saving settings. These 
> settings cause the hard disks to park their heads after a very short 
> inactivity time.
> 
> This hectic parking/deparking activity dramatically shortens the disk's 
> life.
> 
> Said manufacturers apparently take for granted that the OS will set more 
> sensible power saving defaults for the hard disk. Linux distros often 
> don't do this. So it's not exactly a "bug", rather an omission (even 
> though it can be argued that this is not really "Linux's fault").
> 
> 
> ----- DIAGNOSIS -----
> 
> The continued parking/deparking is typically easier to detect on a 
> laptop, where you might hear periodic "clicks" coming from the hard 
> disk.
> 
> A more reliable way is to watch the output of the following `sh` command 
> line, to be issued as root while your system is AC powered (as opposed 
> to battery powered) and not performing disk-intensive tasks:
> 
> while true;do smartctl -a /dev/hda|grep Load_Cycle_Count;sleep 120;done;
> 
> If the last number is constantly increasing every 1 or 2 lines, your 
> system is affected.
> 
> 
> ----- A SOLUTION -----
> 
> The command:
> 
> hdparm -B254 /dev/hda
> 
> changes the primary drive's (/dev/hda) power settings to "almost never 
> park heads". A lower number *might* be desired when running on battery, 
> and an ideal solution would include a way to change that number 
> according to power source (I don't know yet how to do this).
> 
> For the moment, I suggest that the above command be put 
> into /etc/rc.local to make sure it is executed at boot.
> 
> 
> Best regards,
> Andrea Remondini
> 
> 
> 
> 
> ----- NOTES -----
> 
> ¹ <https://bugs.launchpad.net/ubuntu/+source/acpi-support/+bug/59695>
> ² <http://hardware.slashdot.org/article.pl?sid=07/10/30/1742258>



This doesn't seem to work on my desktop system:

[root@localhost ~]# while true; do smartctl -a /dev/hdc |grep 
Load_Cycle_Count; sleep 120; done;

[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                       287G   34G  239G  13% /
/dev/hdc1              99M   28M   67M  30% /boot
tmpfs                 506M     0  506M   0% /dev/shm
[root@localhost ~]#


I left it more than 120 seconds.