“When our RAID array notified us of a failed disk we had no concern as we’ve successfully replaced a disk before. This time there was an error during the rebuild, which caused the array to fail and go offline. Many thanks to DiskEng successfully recovering our data. A thoroughly professional service.”
Lee Hamilton, Reading
A RAID server array, which failed during a rebuild, containing four 2TB HGST hard disk drives arrived at our laboratory from Reading. An examination the drives, revealed no faults with the hardware or the electronics on the drive controller board. Our hard disk data recovery specialists secured sector-by-sector images of all four drives. During the imaging process a handful of unreadable bad sectors on three of the four drives.
All hard disk drives are designed with an inbuilt capacity to deal with bad sectors on a drive, maintaining a list of swapped out sectors. However this list is only finite in size, so that over time it will become exhausted, at which point any new bad sectors becoming apparent to the operating system, or RAID controller. For any set of hard disk drives maintained in the same environment, and sourced from the same supplier, it is fairly common for two or more drives to fill their spare sector list at a similar rate.
An examination of the drive images revealed the RAID configuration being used was RAID 10, a striped mirror set, which means that the bad sectors on the damaged drives will only result in lost data if the same sector within a mirrored pair are unrecoverable. A virtual RAID 10 set was created, which revealed there to be three unrecoverable sectors. It was fortunate that these bad sectors affected some non-critical system areas of the single 4TB NTFS volume. This allowed for a full recovery of the 2.1TB of data files to be returned to the client.