Compaq HSZ80 manual 133, Readaheadcache Default

5–133

READAHEAD_CACHE (Default)

NOREADAHEAD_CACHE

Enables the controller to keep track of read I/Os. If the controller detects sequential read I/Os from the host, it will then try to keep ahead of the host by reading the next sequential blocks of data (those the host has not yet requested) and put the data in cache. This process is sometimes referred to as prefetch. The controller can detect multiple sequential I/O requests across multiple units.

Read ahead caching improves host application performance since the data will be read from the controller cache instead of disk. Read ahead caching is the default for units.

If you do not expect this unit to get sequential I/O requests, select NOREADAHEAD_CACHE for the unit.

RUN (Default)

NORUN

Controls the unit’s operation and availability to the host.

Specify RUN to make a unit available to the host.

Specify NORUN to make a unit unavailable to the host and to cause any data in cache to be flushed to one or more drives. NORUN spins down the devices making up a unit. The drives making up the unit spin down after the data has been completely flushed.

NOTE: Do not specify the RUN and NORUN switches for partitions.

WRITE_PROTECT (Default)

NOWRITE_PROTECT

Tells the controller whether data contained on the unit can be overwritten.

Compaq HSZ80 Array Controller ACS Version 8.3 Configuration and CLI Reference Guide