Hardware and RAID configuration

Buffalo TS-XH4.0TL/R6 with 4x1TB drives in a RAID 6 configuration.

Problem:

The NAS displayed error E13 and E26 and stopped working. The customer performed a firmware update. The NAS then displayed error code E30 (drive malfunctioning).

Diagnosis:

• RAID rotation analysis confirmed a RAID 6 configuration.
• One drive did not belong to the RAID and a second drive was stale. Effectively this was a 4-drive RAID 6 without two drives. A RAID 6 without two drives is recoverable if the algorithm to generate the Q-parity data is known. The algorithm used by this NAS was not published by the manufacturer.
• Our analysis also showed that the RAID hosted an XFS volume. The primary super block of the volume was lost.

Solution:

• We were able to determine that the Q-parity data was based on the widely-used Reed-Solomon encoding scheme.
• We manually recreated the missing XFS metadata.
• We then ran File Scavenger® and recovered the data. File Scavenger® version 4.3 or later supports RAID 6 that uses the Reed-Solomon encoding scheme.

Result:

All files were restored with the original name and folder path.