HP StorageWorks 2300 Family Modular Smart Array CLI reference guide (500912-002, July 2010)

HP StorageWorks 2000 G2 Modular Smart Array CLI Reference Guide 83
set cache-parameters
Description Sets a volume's cache options or the system's cache redundancy mode. Settings you can change
include:
• Cache write policy
• Cache optimization mode
• Cache read-ahead size
• Cache redundancy mode
NOTE: Only change the read-ahead cache settings if you fully understand how the host operating
system, application, and adapter move data so that you can adjust the settings accordingly. Be
prepared to monitor system performance and adjust read-ahead size until you find the optimal size
for your application.
Syntax To set cache options for a specified volume:
set cache-parameters
[write-policy write-back|write-through]
[optimization standard|super-sequential]
[read-ahead-size disabled|default|maximum|64KB|128KB|256KB|512KB|1MB|2MB|4MB
|8MB|16MB|32MB]
volume
Parameters write-policy write-back|write-through
Optional. Sets the cache write policy to either:
• write-back: Write-back caching does not wait for data to be completely written to disk before
signaling the host that the write is complete. This is the preferred setting for a fault-tolerant
environment because it improves the performance of write operations and throughput.
• write-through: Write-through caching significantly impacts performance by waiting for data
to be completely written to disk before signaling the host that the write is complete. Use this
setting only when operating in an environment with low or no fault tolerance.
optimization standard|super-sequential
Optional. Sets the cache optimization mode to either:
• standard: Used for applications that read and write small files in random order, such as
transaction-based and database update applications. Sets the cache block size to 32 KB.
• super-sequential: Used for applications that read and write large files in sequential order,
such as video playback and multimedia post-production video and audio editing applications.
Sets the cache block size to 128 KB.
read-ahead-size
Optional. Controls the use and size of read-ahead cache:
• disable: Turns off read-ahead cache.
• default: Sets one chunk for the first access in a sequential read and one stripe for all
subsequent accesses.
• maximum: Allows the controller to dynamically calculate the maximum read-ahead cache size for
the volume.
• 64KB, 128KB, 256KB, 512KB, 1MB, 2MB, 4MB, 8MB, 16MB, 32MB: Sets a specific cache size.
volume
Name or serial number of the volume to change. For syntax, type Command syntax.