88
Alphabetical list of commands
set cache-parameters
Description
Sets a volume’s cache options. Settings you can change include:
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.
Min. role
manage
Syntax
set cache-parameters
[optimization standard|no-mirror]
[read-ahead-size disabled|adaptive|stripe|512KB|1MB|2MB|4MB|8MB|16MB|32MB]
[write-policy write-back|write-through|wb|wt]
volume
Parameters
optimization standard|no-mirror
Optional. Sets the cache optimization mode:
•
standard
: Optimizes cache for both sequential and random reads. 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 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 non-RAID and RAID-1 vdisks
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
command.
Summary of Contents for AssuredSAN 6004
Page 11: ...Document conventions and symbols 11 TIP Provides helpful hints and shortcuts...
Page 114: ...114 Alphabetical list of commands See also set cli parameters show protocols...
Page 139: ...show controller statistics 139 See also reset all statistics reset controller statistics...
Page 162: ...162 Alphabetical list of commands See also show power supplies...
