Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 150)

Chapter 8. Maintaining Units
138 3ware SATA+SAS RAID Controller Card Software User Guide, Version 10.2
• Migrate-Paused. The unit is in the process of migrating, however
scheduling is enabled, and the present time is not during a scheduled
timeslot. Migrating will start at the next scheduled time slot. Migration is
also paused for up to ten minutes after a reboot, even during a scheduled
timeslot.
• Degraded. One or more drives in the redundant unit is no longer being
used by the controller. For more information, see “About Degraded
Units” on page 138.
• Inoperable. This is a condition where one or more drives are missing
from a unit, causing the unit to no longer be available to the operating
system. Data on an inoperable unit cannot be accessed. For more
information, see “About Inoperable Units” on page 139.
Drive Statuses
The following is a list of drive statuses you may see in 3DM2:
• 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 LSI
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.