I have a WD4100EX and I was running the drives in a raid 5 arrary. We had a power outage and somehow the first 7 sectors of two of the drives are now unreadable. Is there a fix that anyone knows to fix this?
Although RAID5 can handle the case that one whole drive becomes unreadable, RAID5 is unable to handle even minor failures of two or more drives.
Seams that formatting or replacing at least the failed disks and copying the data from the last backup will be necessary.
If these are Advanced Format HDDs (most likely), then they will have a physical sector size of 8 logical sectors (4096 = 8 x 512 bytes). Therefore, one would expect that the first 8 sectors would be unreadable. However, it would be highly unlikely for the first physical sector on two drives to be unreadable, assuming that the other sectors are OK.
If you are using a WD My Cloud PR4100 (WD4100EX) with drives configured in a RAID-5 array, a power outage can sometimes corrupt the RAID metadata stored at the beginning of the disks. The first few sectors of each drive contain important information such as the partition table and RAID superblock. If the first 7 sectors on two drives become unreadable, the NAS may fail to recognize the RAID configuration even though the majority of the data on the disks is still intact.
