HSG80 Array Controller V8.7 Command Line Interface Reference Guide
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ADD UNITS
The controllers only use the PREFERRED_PATH setting if they are in a
dual-redundant configuration. If one controller fails, all the devices are accessed
through the remaining controller ignoring the PREFERRED_PATH setting.
You can specify the PREFERRED_PATH switch for a single controller
configuration; however, the switch will not take effect until you add a second
controller and configure the two controllers for dual-redundancy.
NOTE: If your controllers are configured to operate in transparent-failover mode, do not set
the PREFERRED_PATH switch with the ADD UNITS or SET unit-number
command—otherwise, an error message is generated. This error message will indicate the
assignment of a preferred controller path at the unit level as valid only when operating in
multiple bus failover mode.
•
When no preferred path is assigned, the unit is targeted through the controller
that detects the unit first after the controllers start.
•
Select PREFERRED_PATH=THIS_CONTROLLER to instruct “this
controller” to bring this unit online.
•
Select PREFERRED_PATH=OTHER_CONTROLLER to instruct the “other
controller” to bring this unit online.
NOTE: All partitions on a container must be addressed through the same controller. If you
set PREFERRED_PATH for one partition, all partitions on that container inherit the same
preferred path setting.
READ_CACHE (default)
NOREAD_CACHE
Sets the controller’s read-cache policy function. When READ_CACHE is selected
and the controller receives a read request from the host, the following events
occur: the controller reads the data from the disk drives, delivers it to the host, and
stores the data in its cache module. Subsequent reads for the same data will take
the data from cache rather than access the data from disks.
Read caching improves performance in almost all situations. Therefore, it is
recommended that 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