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HSG80 Array Controller V8.7 Command Line Interface Reference Guide
CLI Command Descriptions
WRITEBACK_CACHE
NOWRITEBACK_CACHE
Enable or disable the write-back data caching function of the controller. The
controller write-back caching feature improves write performance.
NOTE: NOWRITEBACK_CACHE is the default on transportable disks.
WRITEBACK_CACHE is the default on notransportable disks.
•
Specify WRITEBACK_CACHE for all new RAIDsets, mirrorsets, and units
that you want to take advantage of the controller write-back caching feature.
•
Specify NOWRITEBACK_CACHE for units that you want data from the host
to go directly to the specified devices without being cached.
CAUTION: Although there is built-in redundancy to protect data contained in cache,
allowing data to be written to write-back cache may result in the loss of data if the
controller fails.
Specifying NOWRITEBACK_CACHE enables only write-through caching. In
write-through caching, when the controller receives a write request from the host
it places the data in its cache module, writes the data to the disk drives, then
notifies the host when the write operation is complete. This process is called
write-through caching because the data passes through—and is stored in—the
cache memory on its way to the disk drives. Write-through caching is only
enabled when write-back caching is disabled, or when the
MAXIMUM_CACHED_TRANSFER_SIZE switch is set to zero.
NOTE: The controller may take up to five minutes to flush data contained within the
write-back cache when you specify the NOWRITEBACK_CACHE switch.
Examples
To create unit D102 from a single-disk drive named DISK10000, enter:
ADD UNITS D102 DISK10000
•
If the controller pair is in transparent failover mode, this unit is on port 2. It is
presented to each host connection as LUN (2 – offset). Offset is a host
connection characteristic, specified in the ADD (or SET) CONNECTIONS
command.
•
If the controller pair is in multiple-bus failover mode, this unit can potentially
be seen by all four controller ports. It is presented to each host connection as
LUN (2 – offset). Offset is a host connection characteristic, specified in the
ADD (or SET) CONNECTIONS command.