Mylex eXtremeRAID 1100, Installation Manual

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G-10 eXtremeRAID Installation Guide
Striping
Refers to the storing of a sequential block of incoming data across multiple
SCSI drives in a group. For example, if there are 3 SCSI drives in a group,
the data will be separated into blocks and block 1 of the data will be stored
on SCSI drive 1, block 2 on SCSI drive 2, block 3 on SCSI drive 3, block 4
on SCSI drive 1, block 5 on SCSI drive 2 and so on. This storage method
increases the disk system throughput by ensuring a balanced load among all
drives.
System Drives
A system drive is equivalent to a “logical” drive. System drives are presented
to the operating system as available disk drives, each with a capacity
specified by the DAC1164 controller.
Target ID
A target ID is the SCSI ID of a device attached to a DAC1164 controller.
Each SCSI channel can have up to 15 attached SCSI devices (target ID from
0 to 6, and 8 to 15).
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 SCSI drive will receive
the data at a more appropriate time, in order to increase controller
performance. An optional cache battery backup can be used to protect
against data loss as a result of a power failure or system crash.
Write Through Cache
Refers to a caching strategy whereby data is written to the SCSI drive before
a completion status is returned to the host operating system. This caching
strategy is considered more secure, since a power failure will be less likely to
cause loss of data. However, a write through cache results in a slightly lower
performance.