Pegasus R6, R4 Product Manual
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your data to a spare disk drive BEFORE the disk drive fails and your logical drive
goes Critical.
The following actions trigger PDM:
•
A disk drive with unhealthy status (see below)
•
Media Patrol finds a disk critical error
•
You initiate PDM manually
See “Running PDM on a Logical Drive” on page 66.
PDM also counts the number of media errors reported by Media Patrol. 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 have a capacity of 512 reassigned blocks and
2048 error blocks. See “PDM” on page 35.
You can specify the maximum levels for the reassigned and error blocks in PDM
settings. When the table fills to a specified value, PDM triggers a migration of
data from the suspect drive (the disk drive with the bad sectors) to a replacement
physical drive.
During data migration, you have access to your logical drives but they 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 drives.
PDM is enabled on all disk arrays by default. You can disable PDM in the disk
array settings, however that action is not recommended. See “Making Disk Array
Settings” on page 53.
