3Ware 9550SX-4LP User Guide - Page 191

About Verification, About Verifies of Non-Redundant Units

Page 191 highlights

About Background Tasks With the 3ware 9000 series controller, rebuilds on multiple units can take place simultaneously. Rebuilding Units About Verification For the 3ware 9000 series, the verify feature combines verification of redundant units (confirming the validity of the redundant data) and media scans for non-redundant units. (3ware software for the 7000 and 8000 series provided separate features for verify and media scan.) Verification is useful because it can provide early warning of a disk drive problem or failure. For example, if the verification process encounters many error locations, it may be an indication of an excessive number of grown defects on the drive. This allows you to replace drives before they fail. Verifies can be performed through either 3BM (BIOS) or through 3DM. In addition, they can be scheduled to run at preferred times, through 3DM or through the CLI, or can be run automatically during the Verify schedule window, if scheduling and the Auto-verify feature are enabled. For a RAID 1 or RAID 10 unit, a verify compares the data of one mirror with the other. For RAID 5 and RAID 50, a verify calculates RAID 5 parity and compares it to what is written on the disk drive. Verification checks each sector on a drive. This is important, because day-today use of the media may leave many sectors on a drive unused or unchecked for long periods of time. This can result in errors occurring during user operation. Periodic verification of the media allows the disk drive firmware to take corrective actions on problem areas on the disk, minimizing the occurrence of uncorrectable read and write errors. About Verifies of Non-Redundant Units Verification of non-redundant units (single disks, JBODs, spares, and RAID 0 units) read each sector of a drive, sequentially. If a sector can't be read, it is flagged as unreadable, and the next time the controller writes to that location, the drive reallocates the data to a different sector. 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. www.3ware.com 181

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About Background Tasks
www.3ware.com
181
With the 3ware 9000 series controller, rebuilds on multiple units can take
place simultaneously.
Rebuilding Units
About Verification
For the 3ware 9000 series, the verify feature combines verification of
redundant units (confirming the validity of the redundant data) and media
scans for non-redundant units. (3ware software for the 7000 and 8000 series
provided separate features for verify and media scan.)
Verification is useful because it can provide early warning of a disk drive
problem or failure. For example, if the verification process encounters many
error locations, it may be an indication of an excessive number of grown
defects on the drive. This allows you to replace drives before they fail.
Verifies can be performed through either 3BM (BIOS) or through 3DM. In
addition, they can be scheduled to run at preferred times, through 3DM or
through the CLI, or can be run automatically during the Verify schedule
window, if scheduling and the Auto-verify feature are enabled.
For a RAID 1 or RAID 10 unit, a verify compares the data of one mirror with
the other. For RAID 5 and RAID 50, a verify calculates RAID 5 parity and
compares it to what is written on the disk drive.
Verification checks each sector on a drive. This is important, because day-to-
day use of the media may leave many sectors on a drive unused or unchecked
for long periods of time. This can result in errors occurring during user
operation. Periodic verification of the media allows the disk drive firmware to
take corrective actions on problem areas on the disk, minimizing the
occurrence of uncorrectable read and write errors.
About Verifies of Non-Redundant Units
Verification of non-redundant units (single disks, JBODs, spares, and RAID 0
units) read each sector of a drive, sequentially. If a sector can’t be read, it is
flagged as unreadable, and the next time the controller writes to that location,
the drive reallocates the data to a different sector.
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.