CLI Guide

• standard: This controller cache mode of operation is optimized for sequential and random I/O and is
the optimization of choice for most workloads. In this mode, the cache is kept coherent with the partner
controller. This mode gives you high performance and high redundancy. This is the default.
• no-mirror: In this mode of operation, the controller cache performs the same as the standard mode
with the exception that the cache metadata is not mirrored to the partner. While this improves the
response time of write I/O, it comes at the cost of redundancy. If this option is used, the user can expect
higher write performance but is exposed to data loss if a controller fails.
[read-ahead-size disabled|adaptive|stripe|512KB|1MB|2MB|4MB|8MB|16MB|32MB]
Optional. Controls the use and size of read-ahead cache. You can optimize a volume for sequential reads or
streaming data by changing the amount of data read in advance. Read ahead is triggered by sequential
accesses to consecutive logical block address (LBA) ranges. Read ahead can be forward (increasing LBAs) or
reverse (decreasing LBAs).
Increasing the read-ahead size can greatly improve performance for multiple sequential read streams.
However, increasing read-ahead size will likely decrease random read performance.
• disabled: Disables read ahead.
• adaptive: Enables adaptive read-ahead, which allows the controller to dynamically calculate the
optimum read-ahead size for the current workload. This is the default.
• stripe: Sets the read-ahead size to one stripe. The controllers treat NRAID and RAID-1 disk groups
internally as if they have a stripe size of 512 KB, even though they are not striped.
• 512KB, 1MB, 2MB, 4MB, 8MB, 16MB, or 32MB: Sets a specific read-ahead size.
[write-policy write-back|write-through|wb|wt]
Optional. Sets the cache write policy, which determines when cached data is written to the disks. The ability
to hold data in cache while it is being written to disk can increase storage device speed during sequential
reads.
• write-back or wb: 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 or wt: 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
You can configure the write policy to automatically change from write-back to write-through when certain
environmental events occur, such as a fan failure. For details, see help for the set advanced-settings
command.
volume
The name or serial number of the volume to change. A name that includes a space must be enclosed in
double quotes.
volume |all
Specifies either:
• The name or serial number of the volume to change. A name that includes a space must be enclosed in
double quotes.
• all: Apply the changes to all volumes.
Examples
Set the cache policy, optimization mode, and read-ahead size for volume V1.
# set volume-cache-parameters write-policy wb optimization standard read-
ahead-size stripe V1
See also
show cache-parameters
show volumes
set volume-group
Description
Sets the name of a volume group.
Alphabetical list of commands 159