HSG80 Array Controller V8.7 Command Line Interface Reference Guide
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SET unit-number
WRITE_PROTECT
NOWRITE_PROTECT (default)
Specifies whether data contained on the selected unit can be overwritten.
•
Specify WRITE_PROTECT to prevent host write operations to the unit.
However, the controller may still write to a write-protected RAIDset to satisfy
a reconstruct pass or to reconstruct a newly replaced member. Additionally,
metadata, reconstruct, and copy writes are still allowed to RAIDsets and
mirrorsets.
•
Specify NOWRITE_PROTECT to allow the host to write data to the unit. This
allows the controller to overwrite existing data. NOWRITE_PROTECT is the
default for transportable disks.
WRITEBACK_CACHE (default)
NOWRITEBACK_CACHE
Enables or disables the write-back data caching function of the controller. The
controller’s write-back caching feature improves write performance.
•
Specify WRITEBACK_CACHE for all new RAIDsets, mirrorsets, and units to
take advantage of the controller write-back caching feature. This switch
allows the controller to declare the write operation “complete” as soon as the
data reaches its cache memory. The controller performs the slower operation
of writing the data to the disk drives at a later time.
CAUTION: Though there is built-in redundancy in mirrored cache to protect data,
allowing data to be written to write-back cache may result in the loss of data if the
cache fails.
WRITEBACK_CACHE cannot be applied to transportable disks.
The NOWRITEBACK_CACHE switch 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, and then
notifies the host when the write operation is complete. Write-through caching is
enabled only when write-back caching is disabled.
NOWRITEBACK_CACHE is the default on transportable disks.
NOTE: When specifying the NOWRITEBACK_CACHE switch, the controller might take 5
minutes to flush data contained within the write-back cache.