Automatic Acoustic Management
BIG BIG WARNING: THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK!! I HAVE ONLY TESTED IT WITH MY OWN HARDDRIVES AND HAD NO PROBLEMS USING IT. BUT AS I AM NO IDE EXPERT AND THIS IS ONLY BASED ON WHAT I HAVE READ IN THE KERNEL SOURCES I GIVE NO GUARANTEE FOR ANYTHING!!
Most modern harddisk drives have the ability to speed down the head movements to reduce their noise output. The possible values are between 0 and 254. 128 is the most quiet (and therefore slowest) setting and 254 the fastest (and loudest). Some drives have only two levels (quiet / fast), while others may have different levels realized between 128 and 254.
To be able to use this with hdparm, you will need a current kernel with the -ac patches applied. Maybe the kernel of your favorite distribution will already include this (SuSE has it in their current kernel, for example). Just try to compile hdparm, type "hdparm" and have a look for "-M" in the output. If it doesn't appear, your kernel most likely doesn't support it.
You can get the acoustic setting by typing
hdparm -M /dev/hda
To set the most quiet mode use
hdparm -M 128 /dev/hda
For the fastest setting use
hdparm -M 254 /dev/hda
Now test different values and try to hear the difference. :-)
Not all disk drives support this setting - and the speed impacts may also vary between different manufacturers and models.
If you see lines like
kernel: hdb: task_no_data_intr: status=0x51 { DriveReady SeekComplete Error } kernel: hdb: task_no_data_intr: error=0x04 { DriveStatusError }
in your syslog, then your harddisk will most likely not support Acoustic Management.
Perhaps you also wanna have a look on the IBM Feature Tool, available at http://www.storage.ibm.com/hdd/support/download.htm.
I would welcome any feedback to <gernot@hillier.de>
Gernot