About Degraded Units
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Drive Statuses
The following is a list of drive statuses you may see in 3DM:
•
OK.
The drive is fine and is functioning normally.
•
Not Present.
No drive is present in this slot.
•
Drive Removed.
The drive has been removed.
•
Other.
A number of other drive statuses may appear in the event of a
problem. If you have a question about a status shown, contact AMCC
customer support. knowing the exact drive status can help trouble-shoot
the problem.
About Degraded Units
Fault tolerant RAID units provide data redundancy by duplicating
information on multiple drives. These RAID units make it possible to
continue use even if one of the drives in the unit has failed.
•
RAID 1 and RAID 10 units each use mirroring to achieve fault tolerance.
Identical data is stored on two or more drives to protect against drive
failure.
•
RAID 5, RAID 6, and RAID 50 units achieve fault tolerance by using a
simple (exclusive OR) function to generate the parity data that is
distributed on all drives.
•
RAID 6 adds an extra level of protection over RAID 5 by generating a
second parity when data is written. This allows two drives to fail without
compromising data integrity, especially on larger units.
When one of the drives in a fault-tolerant unit fails or is removed or
unplugged, the unit is said to be
degraded
.
You can still read and write data from a degraded unit, but the unit will not be
fault tolerant until it is rebuilt using the Rebuild feature.
When a RAID unit becomes degraded, it is marked as such, and the drive(s)
that failed are marked as
Not In Use
in the 3BM screens and
Degraded
in the
3DM pages. On the 3ware Sidecar, the LED for failed drives turns red.
You should replace the failed drive and rebuild the unit as soon as it is
convenient to do so. The unit will not be fault tolerant until it has been rebuilt.
Rebuilding can occur automatically, depending on your settings. For more
information, see “Rebuilding Units” on page 150.
