Dell PowerVault MD3000i Cli Manual page 92

scan is performed as a background operation and scans all data and
consistency information in defined user virtual disks. A media scan runs on all
virtual disks in the storage array with the following conditions:
• An Optimal status
• No modification operations in progress
• Media scan enabled
• Errors detected during a scan of a user virtual disk are reported to the MEL
and handled as:
– Unrecovered media error — The physical disk could not read the
requested data on its first attempt or on any subsequent retries. For
virtual disks with redundancy protection, the data could not be
reconstructed from the redundant copy. The error is not corrected but
it is reported to the MEL.
– Reconstructed media error — The physical disk could not read the
requested data on its first attempt or on any subsequent retries. The
data is reconstructed from the redundant copy, rewritten to the drive,
verified, and the error is reported to the MEL.
– Recovered media error — The physical disk could not read the
requested data on its first attempt. The result of this action is that the
data is rewritten to the physical disk and verified. The error is reported
to the MEL.
– Consistency mismatches — Consistency errors are found, and a media
error is forced on the block stripe so that it is found when the physical
disk is scanned again. If consistency is repaired, this forced media error
is removed. The result of this action is that the first ten consistency
mismatches found on a virtual disk are reported to the MEL.
– Unfixable error — The data could not be read and consistency
information could not be used to regenerate it. For example,
consistency information cannot be used to reconstruct data on a
degraded virtual disk. The result of this action is that the error is
reported to the MEL.
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Maintaining a Storage Array