what's the recommended hard disk repair tool if the RAID array on my Linux server is corrupted (
I/O errors when listing directories)? Are such
I/O issues recoverable?
Actually, I would recommend
dd_rescue (two different utilities that do similar things) for pulling off all the data you can possibly get from the HD. The wiki I pointed to may contain other useful information as well.
You can basically use these tools to get a disk image of your RAID partition, then
fsck a backup of that image in case some of what was lost was important meta-data. They will try very hard to get as much data as they can from the drive.
Hardware errors can't be repaired with software, sadly.
If you want to recover the data (or just dump it for backup), try TestDisk or just plain ol'