HP MSA 2040 CLI Reference Guide

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Volume cache parameters:
Serial Number
If a volume is specified, its serial number.
Name
If a volume is specified, its name.
Cache Write Policy
If a volume is specified, its cache write policy:
• 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. This is the
default.
• 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.
Cache Optimization
If a volume is specified, its cache optimization mode:
• standard: Optimizes cache for both sequential and random reads. Appropriate for
applications that read and write small files in random order, such as transaction-based and
database update applications. This is the default.
• no-mirror: When this mode is enabled, each controller stops mirroring its cache metadata to
the partner controller. This improves write I/O response time but at the risk of losing data during
a failover. ULP behavior is not affected, with the exception that during failover any write data in
cache will be lost.
Read Ahead Size
If a volume is specified, its read-ahead cache setting:
• Disabled: Read-ahead is disabled.
• Adaptive: Adaptive read-ahead is enabled, which allows the controller to dynamically
calculate the optimum read-ahead size for the current workload.
• Stripe: Read-ahead is set to one stripe. The controllers treat non-RAID and RAID-1 vdisks
internally as if they have a stripe size of 512 KB, even though they are not striped.
• 512 KB, 1 MB, 2 MB, 4 MB, 8 MB, 16 MB, or 32 MB: Size selected by a user.