Lenovo ThinkServer RD330, Software User'S Manual

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Page 397
MegaRAID SAS Software User Guide Appendix C: Glossary
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striping A technique used to write data across all drives in a virtual drive.
Each stripe consists of consecutive virtual drive data addresses that are mapped in
fixed-size units to each drive in the virtual drive using a sequential pattern. For
example, if the virtual drive includes five drives, the stripe writes data to drives one
through five without repeating any of the drives. The amount of space consumed by a
stripe is the same on each drive. Striping by itself does not provide data redundancy.
Striping in combination with parity does provide data redundancy.
subvendor ID A controller property that lists additional vendor ID information about the controller.
uncorrectable error count A controller property that lists the number of uncorrectable errors detected on drives
connected to the controller. If the error count reaches a certain level, a drive will be
marked as failed.
vendor ID A controller property indicating the vendor-assigned ID number of the controller.
vendor info A drive property listing the name of the vendor of the drive.
virtual drive A storage unit created by a RAID controller from one or more drives. Although a virtual
drive can be created from several drives, it is seen by the operating system as a single
drive. Depending on the RAID level used, the virtual drive can retain redundant data in
case of a drive failure.
virtual drive state A virtual drive property indicating the condition of the virtual drive. Examples include
Optimal and Degraded.
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 of the data in a drive write
transaction. Data is written to the drive 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, and elapsed time from the last cache flush.
write policy See Default Write Policy .
write-through In Write-Through Caching mode, the controller sends a data transfer completion signal
to the host when the drive subsystem has received all of the data and has completed
the write transaction to the drive.