>>> On Tue, 17 Jan 2012 01:09:34 +0100, Wim Delvaux
>>> <wrl.delvaux@xxxxxxxxx> said:
> Hi all, I have two 2TB disks half set up using raid 1 (full
> mirroring ?) and the other half using striping. very
> frequently my system, a kubuntu 11.10, hangs (gui is
> unresponsive). pressing alt-esc to popup the process monitor
> shows that key processes are hanging on disk-sleep. Often this
> is the flush daemon or the mdadm processes or sometimes just
> two or three applications.
It could be many different reasons. You should check 'dmesg' and
run run 'vmstat 1' in a window while this happens.
Most likely causes:
- Your 2TB disks have long fixed error recovery timeouts and
some sectors are going bad. In this case there is no fix
other than replacing the disks.
- The disks literally go to 'sleep' (that is power-saving
mode). The fix here is to specify 'hdparm -S 0'.
- The disk elevator keeps starving reads or writes during high
disk activity. The fix here is to use 'deadline' which is
known to have fewer starvation bugs than others.
- A lot of unwritten pages are allowed to accumulate in
memory, and the flush daemon and other applications hang
while they are being written out. The fix here is to specify
a small value for 'dirty_background_ratio' (like 1 or 2) and
a large one for 'dirty_ratio' (like 40 or 50), or equivalent
'_bytes'.
- Since you have 8GiB of RAM, this is least likely: high
traffic on the swap space combined with the very bad page
swap logic in the Linux kernel.
Usually it is large values of 'dirty_background_ratio' on
large-memory configurations.
[ ... ]
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
