Dell PowerVault MD3420 - Manual (Page 115)

10
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.
115