Promise Technology 2-Year Extended Warranty for VessR2000 RAID Head User Manual

Page 577

550

Vess R2000 Series Product Manual

Promise Technologies

•

Paused

– Temporary pause while another background

runs. Or a pause initiated by the user.

PdM

Predictive Data Migration (PDM) is the migration of data from the suspect phyi-cal drive to a spare drive,

similar to rebuilding a logical drive. But unlike Re-building, PDM constantly monitors your physical drives and

automatically copies your data to a spare drive before the physical drive fails and your logical drive goes Critical.

The following actions trigger PDM:

• A phyical drive with unhealthy status (see below)

• Media Patrol finds a critical error

• You initiate PDM manually

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 physical drive

creates a map around it. These maps are saved in the bad sector remapping table, which has a capacity of 512

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 physical

drives.

PDM is enabled on all disk arrays by default. You can disable PDM in the disk array settings, however that action