HP Array Controller HSG V8.7 Software - Manual (Page 303)

CLI Commands B–31
READ_CACHE (Default)
NOREAD_CACHE
Sets the controller’s cache read policy function. Read caching improves
performance in almost all situations. Therefore, it is recommended you
leave its default setting, READ_CACHE enabled. However, under
certain 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 the read cache function
and remove the processing overhead associated with caching data.
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 are adding a unit that is not expected to get sequential I/O
requests, select NOREADAHEAD_CACHE for the unit.
RUN (Default)
NORUN
Controls the unit’s 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 all the disks used in the 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.