Owner manual

9
Maintaining A Storage Array
Maintenance covers a broad spectrum of activities. Its goal is to keep a storage array operational and available to all
hosts. This chapter provides descriptions of command line interface (CLI) and script commands that you can use to
perform storage array maintenance. The commands are organized into four sections:
• Routine maintenance
• Performance tuning
• Troubleshooting and diagnostics
• Recovery operations
The organization is not a rigid approach, and you can use the commands as appropriate for your storage array. The
commands listed in this chapter do not cover the entire array of commands you can use for maintenance. Other
commands, particularly the set commands, can provide diagnostic or maintenance capabilities.
Routine Maintenance
Routine maintenance involves those tasks you might perform periodically to ensure that the storage array is running as
well as possible or to detect conditions before they become problems.
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 drive 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.
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