Dell PowerVault MD 32XX/36XX Series Storage Arrays CLI Guide

Running A Media Scan

Media scan provides a method of detecting physical disk media errors before they are found during a normal read from or write to the physical disks. Any errors detected are reported to the Major Event Log (MEL). Media scan provides an early indication of a potential virtual disk failure and reduces the possibility of encountering a media error during host operations. A media scan is performed as a background operation and scans all data and consistency information in defined user virtual disks or snapshot groups.

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.

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)

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Dell PowerVault MD 32XX/36XX Series Storage Arrays CLI Guide

Running A Media Scan

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