Specifications

7–130 CLI Commands
Read caching improves performance in almost all situations, so it is generally
recommended to leave it enabled. However, under certain types of conditions, such as
when performing a backup, read-caching may not be necessary since only a small
amount of data is cached. In such instances, it may be beneficial to disable read cache
and remove the processing overhead associated with caching.
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 disk drive’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 partitioned units.
WRITE_PROTECT
NOWRITE_PROTECT (Default)
Assigns to the unit’s a write-protect policy.