Dell PowerVault MD3420 - Manual (Page 116)

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.
The script command set provides four commands to define media scan properties:
• set virtualDisks
• set storageArray
• set snapGroup
• set snapVirtualDisk
The set virtualDisk command enables a media scan for the virtual disk. The following syntax is the
general form of the command:
set (allVirtualDisks | virtualDisk
[virtualDiskName] | virtualDisks [virtualDiskName1
... virtualDiskNamen] | virtualDisk <wwid>
mediaScanEnabled=(TRUE | FALSE)
The set storageArray command defines how frequently a media scan is run on a storage array. The
following syntax is the general form of the command:
set storageArray mediaScanRate=(disabled | 1-30)
The set snapVirtualDisk and set snapGroup commands run media scans on physical disks that
are members of snapshots and snapshot groups. The following examples show command syntax:
set snapVirtualDisk ["snapvirtualDiskName"]
mediaScanEnabled=(TRUE | FALSE)
set snapGroup ["snapGroupName"]
mediaScanEnabled=(TRUE | FALSE)
Running A Consistency Check With A Media Scan
Consistency checks are performed when media scans are run, if consistency check is enabled on the
virtual disk. During a consistency check, all data blocks in a virtual disk are scanned, and deteriorated data
is corrected. The method of correction depends on the redundant array of independent disks (RAID)
levels:
RAID 5 and
RAID 6 virtual
disks Consistency is checked and repaired.
RAID 1 virtual
disks The data is compared between the mirrored physical disks, and data
inconsistencies are repaired.
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