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46 Planning: MD3600f Series Storage Array Terms and Concepts
Background Initialization
The storage array executes a background initialization when the virtual disk is
created to establish parity, while allowing full host server access to the virtual
disks. Background initialization does not run on RAID 0 virtual disks. The
background initialization rate is controlled by MDSM. To change the rate of
background initialization, you must stop any existing background
initialization. The rate change is implemented when the background
initialization restarts automatically.
Foreground Initialization
The storage array supports foreground initialization for virtual disks. All
access to the virtual disk is blocked during foreground initialization. During
foreground initialization, zeros (0x00) are written to every sector of the virtual
disk. The virtual disk is available after foreground initialization is completed.
Consistency Check
A consistency check verifies the correctness of data in a redundant array
(RAID levels 1, 5, 6, and 10). For example, in a system with parity, checking
consistency involves computing the data on one physical disk and comparing
the results to the contents of the parity physical disk.
A consistency check is similar to a background initialization. The difference is
that background initialization cannot be started or stopped manually, while
consistency check can.
NOTE: It is recommended that you run data consistency checks on a redundant
array at least once a month. This allows detection and automatic replacement of
unreadable sectors. Finding an unreadable sector during a rebuild of a failed
physical disk is a serious problem, because the system does not have the
redundancy to recover the data.
Media Verification
Another background task performed by the storage array is media verification
of all configured physical disks in a disk group. The storage array uses the
Read operation to perform verification on the space configured in virtual
disks and the space reserved for the metadata.
book.book Page 46 Wednesday, June 8, 2011 5:01 PM