3Ware 9550SX-4LP User Guide - Page 192

Chapter 9. Maintaining Units 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 Drive ECC error reported" on page 232.) 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 these types of configuration changes: • RAID level • Unit capacity expansion • Change to stripe size 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. Once a unit is put into the migration state, it must be allowed to complete the process. While migrating, rebuilds or verifies to the unit are not permitted. Migrate tasks are always done in the background, and can be initiated through either 3DM or the CLI. (Foreground migrations through 3BM are not supported.) 182 3ware Serial ATA RAID Controller User Guide