Dell PowerEdge RAID Controller 6i - Manual (Page 152)

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Glossary
Stripe Element Size
The total disk space consumed by a stripe not including a parity disk. For
example, consider a stripe that contains 64 KB of disk space and has 16 KB of
data residing on each disk in the stripe. In this case, the stripe element size is
16 KB and the stripe size is 64 KB.
Striping
Disk striping writes data across all physical disks in a virtual disk. Each stripe consists
of consecutive virtual disk data addresses that are mapped in fixed-size units to each
physical disk in the virtual disk using a sequential pattern. For example, if the virtual
disk includes five physical disks, the stripe writes data to physical disks one through
five without repeating any of the physical disks. The amount of space consumed by
a stripe is the same on each physical disk. The portion of a stripe that resides on a
physical disk is a stripe element. Striping by itself does not provide data redundancy.
Striping in combination with parity does provide data redundancy.
V
Virtual Disk
A virtual disk refers to storage created by a RAID controller from one or more
physical disks. Although a virtual disk may be created from several physical
disks, it is seen by the operating system as a single disk. Depending on the RAID
level used, the virtual disk may retain redundant data in case of a disk failure.
W
Write-Back
In Write-Back caching mode, the controller sends a data transfer completion signal
to the host when the controller cache has received all the data in a disk write
transaction. Data is written to the disk subsystem in accordance with policies set up
by the controller. These policies include the amount of dirty/clean cache lines, the
number of cache lines available, elapsed time from the last cache flush, and others.
Write-Through
In Write-Through caching mode, the controller sends a data transfer completion
signal to the host when the disk subsystem has received all the data and has
completed the write transaction to the disk.
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