3Ware 9550SXU16MLB10 User Guide - Page 129

About Verifies of Redundant Units, How Errors Are Handled, About Migration

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About Background Tasks About Verifies of Redundant Units Verifies of redundant units also read each sector, working from lowest block to highest block. If verification cannot read data in a sector, dynamic sector repair is used to recover the lost data from the redundant drive or drives; this recovered data is written to the problem sector. This forces the drive to reallocate the defective sector with a good spare sector. How Errors Are Handled Verification makes use of the same error checking and error repair techniques used during ordinary use of drives configured through 3ware RAID controllers. When verification encounters an error, the controller typically retries the command. If there are cable CRC errors, there may be multiple retries including downgrade of the UDMA mode. If the error persists and is unrepairable (e.g., ECC errors), an error notification is issued to indicate the problem. (See "AEN 026h AEN_DRIVE_ECC_ERROR" on page 169.) If the disk drive is part of a redundant array that is in a redundant state (not DEGRADED or REBUILDING), then Dynamic Sector Repair automatically rewrites the redundant data to the error location to force the drive to reallocate the error location. A notification of repair is posted. The result is a restoration of drive and data integrity; the primary and redundant data are again both valid. If the array is not redundant, a file-system check is recommended to correct the issue. If the errors persist and cannot be overwritten from a backup copy, perform a final incremental backup. You will need to replace the defective drive, recreate the array, and reinstall the data. About Migration Migration allows on-line units to be reconfigured. You can make two types of configuration changes: „ RAID Level „ Unit Capacity Expansion RAID level migration and unit capacity expansion tasks can be done together or separately. Migration tasks follow the same schedule as rebuild and initialization tasks. Because of the controller and disk resources required during migration, when migration is active, it has priority over other background tasks. When migration starts, it will take the highest priority over rebuild, initialize and verify. www.3ware.com 123

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About Background Tasks
www.3ware.com
123
About Verifies of Redundant Units
Verifies of redundant units also read each sector, working from lowest block
to highest block. If verification cannot read data in a sector, dynamic sector
repair is used to recover the lost data from the redundant drive or drives; this
recovered data is written to the problem sector. This forces the drive to
reallocate the defective sector with a good spare sector.
How Errors Are Handled
Verification makes use of the same error checking and error repair techniques
used during ordinary use of drives configured through 3ware RAID
controllers.
When verification encounters an error, the controller typically retries the
command. If there are cable CRC errors, there may be multiple retries
including downgrade of the UDMA mode. If the error persists and is
unrepairable (e.g., ECC errors), an error notification is issued to indicate the
problem. (See “AEN 026h AEN_DRIVE_ECC_ERROR” on page 169.)
If the disk drive is part of a redundant array that is in a redundant state (not
DEGRADED or REBUILDING), then Dynamic Sector Repair automatically
rewrites the redundant data to the error location to force the drive to reallocate
the error location. A notification of repair is posted. The result is a restoration
of drive and data integrity; the primary and redundant data are again both
valid.
If the array is not redundant, a file-system check is recommended to correct
the issue. If the errors persist and cannot be overwritten from a backup copy,
perform a final incremental backup. You will need to replace the defective
drive, recreate the array, and reinstall the data.
About Migration
Migration allows on-line units to be reconfigured. You can make two types of
configuration changes:
RAID Level
Unit Capacity Expansion
RAID level migration and unit capacity expansion tasks can be done together
or separately.
Migration tasks follow the same schedule as rebuild and initialization tasks.
Because of the controller and disk resources required during migration, when
migration is active, it has priority over other background tasks. When
migration starts, it will take the highest priority over rebuild, initialize and
verify.