VTRAK M-CLASS Product Manual

VTrak M-Class Product Manual
258
A disk drive becomes unhealthy when:
• A SMART error is reported
• The bad sector remapping table fills to the specified level
Because data would be lost if written to a bad sector, when a bad sector is
detected, the disk drive creates a map around it. These maps are saved in the
bad sector remapping table, which has a capacity of 512 reassigned blocks and
1024 error blocks.
When the table fills to a specified percentage of its capacity, PDM triggers a
migration of data from the suspect drive (the disk drive with the bad sectors) to a
spare disk drive.
During data migration, you will have access to the Logical Drive but it will respond
more slowly to read/write tasks because of the additional operation. The time
required for data migration depends on the size of the disk drive.
See “Logical Drive PDM” on page 147.
Transition
The Transition feature enables you to specify “permanent” spare drives for your
VTrak subsystem. Transition is the process of replacing a revertible spare drive
that is currently part of a disk array with an unconfigured physical drive or a non-
revertible spare. The revertible spare drive returns to its original status.
Transition happens automatically when the following sequence of events takes
place:
• You create a revertible spare drive.
See page 151 (WebPAM PROe) or page 202 (CLU).
• A physical drive assigned to your disk array fails and the array goes critical
or degraded.
• VTrak automatically rebuilds your array to the revertible spare drive and the
array becomes functional again.
• You replace the failed physical drive with a new physical drive of equal or
greater capacity.
• VTrak automatically transitions (moves) the data from the revertible spare to
the new physical drive.
• The new physical drive becomes part of the array and the revertible spare
drive returns to its original spare status.
Transition happens manually when you specify a different unconfigured physical
drive to transition (move) the data from the revertible spare drive.
See the example below.