I'm running Ubuntu 11.04 on a software RAID1 and experience the occasional 'system hang' during extended I/O.
With' system hang' I mean the sytem is still up but accepts no input and logs no kernel/system messages and is for all intent and purposes dead until a reboot.
With extended I/O I mean full backups (400GB+), a full check on the array, etc.
I have logged this as an Ubuntu bug, but given that I have configured 10+ other systems the same and have never seen this problem, nobody else seems to have a similar problem, I'm looking for other possible reasons for this behaviour.
One possibility would be the controller. I'm running a GIGABYTE GA-MA790FXT-UD5P motherboard and the disks are controlled by a AMD SB750 controller
I had a similar issue with Gigabyte A75-UD4H and A8-3850 CPU, I did all of that:
1. Updated BIOS: problem seemed to persist, but got better.
2. Tried to install drivers from AMD directly: problem persisted.
3. Installed fglrx-updates package (for drivers)
4. Unmounted CPU cooler and added more thermal compound (this reduced temperature by around 5º or so, not significant).
5. Installed newer kernel (3.0.8) compiled myself.
In the end, the problem went away.... I think it was the newer video drivers + newer kernel.