HP LH4r HP NetServer FCArray Assistant - Installation and User Guide - Page 162

System Drive Affinity, System Drives, Target ID, Write Back Cache, Write Through Cache

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Appendix B Glossary into blocks. Block 1 of the data will be stored on drive 1, block 2 on drive 2, block 3 on drive 3, block 4 on drive 1, block 5 on drive 2 and so on. This storage method increases the disk system throughput by ensuring a balanced load among all drives. System Drive Affinity See "LUN Mapping." System Drives See "Logical Drives." Target ID A target ID is the ID of a device attached to a controller. Write Back Cache Refers to a caching strategy whereby write operations result in a completion signal being sent to the host operating system as soon as the cache (not the disk drive) receives the data to be written. The target drive will receive the data at a more appropriate time, in order to increase controller performance. An optional cache battery backup or an Uninterruptable Power Supply (UPS) can be used to protect against data loss as a result of a power failure or system crash during the time the data is only in the cache. Write Through Cache Refers to a caching strategy whereby data is written to the drive before completion status is returned to the host OS. This caching strategy is considered more secure, since a power failure is less likely to cause loss of data. However, a write through cache results in a slightly lower performance. 156

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Appendix B
Glossary
156
into blocks. Block 1 of the data will be stored on drive 1, block 2 on drive 2, block
3 on drive 3, block 4 on drive 1, block 5 on drive 2 and so on. This storage method
increases the disk system throughput by ensuring a balanced load among all
drives.
System Drive Affinity
See "LUN Mapping."
System Drives
See "Logical Drives."
Target ID
A target ID is the ID of a device attached to a controller.
Write Back Cache
Refers to a caching strategy whereby write operations result in a completion signal
being sent to the host operating system as soon as the cache (not the disk drive)
receives the data to be written. The target drive will receive the data at a more
appropriate time, in order to increase controller performance. An optional cache
battery backup or an Uninterruptable Power Supply (UPS) can be used to protect
against data loss as a result of a power failure or system crash during the time the
data is only in the cache.
Write Through Cache
Refers to a caching strategy whereby data is written to the drive before completion
status is returned to the host OS. This caching strategy is considered more secure,
since a power failure is less likely to cause loss of data. However, a write through
cache results in a slightly lower performance.