Dell (PERC) S100, PERC S300 - page 110

110 Glossary
S TRIPING —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.
TB (
TERABYTE )—One thousand gigabytes (approximately one trillion bytes).
T
RANSFORMATION —A transformation can mean: (1) Capacity expansion, using
OCE (adding more physical disks to a virtual disk and increasing the storage capacity
of the virtual disk or virtual disks), or (2) Rebuilding (rebuilding data on the virtual
disk from a redundant virtual disk or from a hot spare or backup physical disk).
V
IRTUAL D ISK —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
RITE -C ACHE E NABLE —In Write-cache enable 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. The VD cache is disabled by default, but can be
enabled by the user through the user interface. The risk of using Write-cache enable is
that the cached data can be lost if there is a power failure before it is written to the
storage device. This risk can be mitigated by using a Uninterrupted Power Supply
(UPS) on PERC S100 or S300 system. A UPS is recommended for use if the cache is
enabled.
W
RITE -C ACHE D ISABLE —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.
WHQL (W
INDOWS H ARDWARE Q UALITY L ABS )—A Microsoft Corporation facility
that provides testing services for non-Microsoft hardware and device drivers, to ensure
compliance and compatibility with Microsoft operating systems.
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