Comment 12 for bug 270794

I believe i've found the problem (it's been a week without the disk freezing ... and i've been doing a lot of tests under heavy load).

It seems that the problem is related to "pdflush", i guess the default parameters (the ones that came with my original Ubuntu installation (first 8.04 and later 8.10) could use some tunning.

I noticed (... "cat /proc/meminfo") that the "Dirty" values grow until almost reach 40000 kB (my PC RAM = 1 GB) and stay like that for too much time before they were cleaned. I guessed that for some unknown reason "pdflush" wasn't cleaning the "Dirty" area as frequently as it was needed.

So I modified the "/etc/sysctl.conf" in order to have "pdflush" activated more frequently (... added the following lines) :
vm.dirty_writeback_centisecs = 200
vm.dirty_expire_centisecs = 400

... A system reboot and no more freezing ... (just to be safe a prior "fsck" to clean previous problems caused by previous freezings).

Note :
1. For info about "The Linux Page Cache and pdflush" I found this :
http://hi.baidu.com/pkubuntu/blog/item/d7413c01c8747b0b7bec2c9e.html

2. It's not needed to alter the "/etc/sysctl.conf" file and reboot the system to change the "pdflush" parameters, it can be done (for testing purposes) by issuing the following commands ( ... must be root) :
echo 200 > /proc/sys/vm/dirty_writeback_centisecs
echo 400 > /proc/sys/vm/dirty_expire_centisecs

3. I've seen in the forum other Bug reports related to sata disks and freezes that might be solved by fine tunning the "pdflush parameters" ... does it means that the default "pdflush" parameters are not the best values for those users with sata disks ???