Try the following steps:
- Turn off the system and remove the “available” disk.
- Enter Intel® RAID Option Rom by pressing Ctrl + I during POST, before the operating system boots. Does the RAID 5 volume appear as “Degraded”?
- Turn off the system again and install the “available” disk. Make sure it is connected to a SATA port that belongs to the ICH10R (instead of third party SATA controller).
- Check again for the status of the disk and the RAID volume.
If the status of the RAID volume is “Degraded” there might be a problem with one of the member disks; however, if the status is “Failed” the RAID structure is damaged and it is not recoverable.
No, this didn't help - both before and after step 2 RAID5 is seen as Failed.
However, I managed to solve it following a (rather risky) guideline found somewhere on the net.
Basically, it involved destroying an entire array, re-creating it with exactly the same parameters and disk order, and using TestDisk recovery tool to find and recreate exactly same partitions.
Miraculously, it worked.