Dell 6 series, User Manual

Page: 155 / 160

Glossary
155
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.
Dell_PERC6.2_UG.book Page 155 Wednesday, June 24, 2009 6:08 PM