Mylex DAC960PG, Installation Manual

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Functional Description
Manual No. 771971 2-23
Cache Management
The DAC960PG provides performance enhancement of data transfers
through its on-board cache memory. The controller supports cache memory
sizes from 4 MB (minimum) to 128 MB (maximum). Cache memory is
allocated by the controller memory management functions for Read Cache
and Write Cache. Write cache policy is user-selectable for each logical unit
to achieve optimum performance within specific applications.
Read Cache
Read cache is always enabled by the controller. Its operation is transparent
and requires no user intervention.
Write-Back Cache
Write-Back Cache refers to a caching strategy whereby write operations
result in a completion status 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.
Write-Through Cache
Write-Through Cache refers to a cache writing 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 in most applications.
Cache Battery Backup
An optional cache battery backup is available that can be used to protect
against cache data loss in the event of a power failure.