The 3ware RAID controller supports a feature called dynamic sector repair that allows the unit to recover from certain drive errors that would normally result in a degraded unit situation. For redundant units such as RAID 1, 5, 6, 10, and 50, the 3ware RAID controller essentially has two copies of your data available. If a read command to a sector on a disk drive results in an error, it reverts to the redundant copy in order to satisfy the host’s request. At this point, the 3ware RAID controller has a good copy of the requested data in its cache memory. It will then use this data to force the failing drive to reallocate the bad sector, which essentially repairs the sector.

Sector repairs are an indication of the presence of grown defects on a particular drive. While typical modern disk drives are designed to allow several hundred grown defects, special attention should be paid to any drive in a unit that begins to indicate sector repair messages. This may be an indication of a drive that is beginning to fail. You may wish to replace the drive, especially if the number of sector repair errors exceeds 3 per month.