Apple RAID Utility - Manual (Page 13)

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The current state of the battery is also indicated by the icon in the lower-left corner of
the RAID Utility window.
If a Volume is Degraded
A degraded volume is either not providing full performance or has lost its ability to
guarantee data protection. All data on a degraded volume is available, but data will be
lost if a disk fails. A volume’s status is listed as degraded:
 While the volume is being created. This is normal, and the volume’s status changes
from degraded to good as soon as initialization is finished.
 When a disk fails in the RAID 1, RAID 5, or RAID 0+1 set that the volume is based on.
The volume remains in a degraded state until you replace the faulty drive or until an
available spare is integrated into the RAID set.
 While the RAID set that the volume is based on is recovering from a loss of data
redundancy. The volume’s status changes from degraded to good as soon as the
recovery process in finished.
If a Disk Fails
If a RAID set or volume becomes degraded because a disk has failed, you can use RAID
Utility to identify the disk that needs to be replaced.
Note: If your RAID setup includes a spare drive, it is automatically incorporated into the
RAID set, and the set switches from degraded to good as soon as the recovery process
finishes. If there is no spare, the set will remain degraded until you replace the failed
drive, and if a second drive fails before you replace the first, you could lose data.
To replace a failed disk:
1 Open RAID Utility, select the RAID set or volume that is displaying a problem status
indicator, and look for a drive bay with a red status indicator.
The bay numbers in RAID Utility correspond to the numbered drive bays in your Mac
Pro or Xserve.
2 Replace the bad drive module.
3 Use the Make Spare command to set up the new drive as a global spare.
If no spare was available when the original drive failed, the RAID card uses the new
spare immediately to rebuild the affected RAID set and volumes. If a spare was
available at the time of the failure, it is already incorporated into the affected RAID set,
and the new spare remains available until it is needed.
If SMART Status is Listed as Unsupported
Self-Monitoring, Analysis, and Reporting Technology (SMART) status information is
available only for SATA drives. If you are using SAS drives, SMART is listed as
unsupported in the drive information in RAID Utility.