Installation manual

34
RAID Media Scan Feature
The Media Scan feature scans disk drives for media
errors and parity errors. All media errors are counted
and fixed. All parity errors are reported in the event log.
The two options are described below:
Media Scan - Media Scan works with parity RAID group
members, Hot Spare drives and unallocated drives.
Media Scan reads the selected drives and, if a Media
Error is found, Media Scan re-writes the disk with the
media error. The drive will relocate the bad sector to an
alternate part of the drive. Media Scan re-writes the
correct data for a disk that is a member of an on-line parity
RAID group. Media Scan writes random data to Hot Spare
drives and unallocated drives. The Media Scan feature
records the number of media errors detected and
corrected for each drive. These counts are stored
persistently if the drive is a RAID group member or a Hot
Spare drive. The counts are not persistently stored for any
other drives.
Media Scan with Parity Verify - is a variation of Media
Scan that is available for on-line parity RAID groups only.
Parity Verification is performed on each RAID group
stripe that has no detected media errors. The parity of the
stripe is recalculated and compared to the original parity
for the stripe. If there is a mismatch, an error is generated
and recorded in the Event Log and System Log files.
Modes of operation for:
• On-line RAID Group – Media Scan performs
SCSI Read commands to each stripe group.
Parity verification is performed on a stripe that
has no media errors. Media Scan activity is
scheduled in accordance with the Rebuild
Priority Level. Media Scan is restarted after
reboot if the Media Scan did not complete.
• Degraded or Offline RAID Group – Media Scan
performs SCSI Read commands for each stripe
group of the on-line drives. No parity verification
occurs. The Media Scan is restarted after a re-
boot if the Media Scan did not complete.
• Hot Spares & Unallocated Drives – Media Scan
performs SCSI Read commands for each
selected drive. Media Scan is not restarted after
a re-boot if the Media Scan did not complete.