Dell PowerEdge RAID Controller 6i - Manual (Page 148)

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Glossary
Read-Ahead
A memory caching capability in some controllers that allows them to read
sequentially ahead of requested data and store the additional data in cache
memory, anticipating that the additional data is required soon. Read-Ahead
supplies sequential data faster, but is not as effective when accessing random data.
Rebuild
The regeneration of all data to a replacement disk in a redundant virtual disk
(RAID level 1, 5, 6, 10, 50, or 60) after a physical disk failure. A disk rebuild
normally occurs without interrupting normal operations on the affected virtual
disk, though some degradation of performance of the disk subsystem can occur.
Rebuild Rate
The percentage of central processing unit (CPU) resources devoted to
rebuilding.
Reconstruct
The act of remaking a virtual disk after changing RAID levels or adding a
physical disk to an existing virtual disk.
Redundancy
The provision of multiple interchangeable components to perform a single
function to cope with failures and errors. Common forms of hardware redundancy
are disk mirroring, implementations of parity disks, or distributed parity.
Redundant Virtual Disk
A redundant virtual disk is one which has redundant data on physical disks in
the disk group that can be used to rebuild a failed physical disk. A virtual disk
can use disk striping across the physical disks, disk mirroring or parity to provide
redundancy. This offers protection in case of a physical disk failure.
Replace Member
The procedure used to copy data from a source physical disk of a virtual disk to a
target physical disk that is not a part of the virtual disk. The Replace Member
operation 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). The Replace Member operation can be run automatically or manually.
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