SCSI Physical Drive Used Reallocation Sectors. This shows the number of sectors of the reallocation area that have been used by the physical drive over the life of the drive. Because of the nature of magnetic disks, certain sectors on a drive may have media defects. The reallocation area is part of the disk drive that the drive manufacturer sets aside to compensate for these defects. The drive writes information addressed from these unusable sectors to available sectors in the reallocation area. If all of the reserved sectors have been used, then there is no way for the drive to remap bad sectors and the drive will start failing. Unfortunately, the number of reallocation sectors originally reserved for this purpose is drive specific and you must contact the drive vendor for these values. If the current value starts to approach the maximum reserved you may wish to replace the drive before it fails.