1.1 Basics
It is recommended that you perform a consistency check at least once a month.
Copyback
The copyback feature allows you to copy data from a source disk of a logical drive to a
destination disk that is not a part of the logical drive. Copyback is often used to create
or restore a specific physical configuration for an array (for example, a specific
arrangement of array members on the device I/O buses). Copyback can be run
automatically or manually.
Typically, when a disk fails or is expected to fail, the data is rebuilt on a hot spare. The
failed disk is replaced with a new disk. Then the data is copied from the hot spare to
the new disk, and the hot spare reverts from a rebuild disk to its original hot spare
status. The copyback operation runs as a background activity, and the logical drive is
still available online to the host.
Copyback is also initiated when the first Self-Monitoring Analysis and Reporting
Technology (SMART) error occurs on a disk that is part of a logical drive. The
destination disk is a hot spare that qualifies as a rebuild disk. The disk with the SMART
error is marked as failed only after the successful completion of the copyback. This
avoids putting the array in degraded status.
Background Initialization (BGI)
Background initialization is a consistency check that is forced when you create a
virtual drive. This is an automatic operation that starts 5 minutes after you create the
virtual drive.
Background initialization is a check for media errors on the disks. It ensures that
striped data segments are the same on all disks in a drive group. The default and
recommended background initialization rate is 30 percent. Before you change the
rebuild rate, you must stop the background initialization or the rate change will not
affect the background initialization rate.
Patrol Read
Patrol read involves the review of your system for possible disk errors that could lead
to disk failure and then action to correct errors. The goal is to protect data integrity by
detecting disk failure before the failure can damage data. The corrective actions
depend on the array configuration and the type of errors.
Patrol read starts only when the controller is idle for a defined period of time and no
other background tasks are active, though it can continue to run during heavy I/O
processes.
MegaRAID® CacheCade™ Pro 2.0
MegaRAID CacheCade Pro 2.0 read/write software eliminates the need for manually
configured hybrid arrays by intelligently and dynamically managing frequently
accessed data and copying it from HDD volumes to a higher performance layer of SSD
cache. Copying the most accessed data (‘hot spot’) to flash cache relieves the primary
HDD array from time-consuming transactions which allows for more efficient hard disk
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