Silicon Graphics InfiniteStorage 4000 Series, Настройка и обслуживание

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78 Modifying Your Configuration
The
writeCacheEnabled
parameter turns on or turns off the ability of the host to
write data to the cache. Write caching enables write operations from the host to be
stored in cache memory. The volume data in the cache is automatically written to the
drives every 10 seconds. To enable write caching, set this parameter to
TRUE
. To
disable write caching, set this parameter to
FALSE
. This example shows how to set
this parameter:
c:\...\sm X \client>smcli 123.45.67.88 123.45.67.89

-c “set allVolumes writeCacheEnabled=TRUE;”
The
cacheReadPrefetch
parameter turns on or turns off the ability of the
controller to read additional data blocks into cache. When you turn on cache read
prefetch, the controller copies additional data blocks into cache while it is reading
requested data blocks from a drive into cache. This action increases the chance that a
future request for data can be fulfilled from the cache, which improves the speed with
which data is accessed. The number of additional data blocks that the controller reads
into cache is determined by the storage array configuration settings that you use.
Cache read prefetch is important for applications that use sequential I/O, such as
multimedia applications.
Valid values for the
cacheReadPrefetch
parameter are
TRUE
or
FALSE
. If you
want to turn on cache read prefetch, set the
cacheReadPrefetch
parameter to
TRUE
. If you want to turn off cache read prefetch, set the
cacheReadPrefetch
parameter to
FALSE
. This example shows how to set this parameter:
c:\...\sm X \client>smcli 123.45.67.88 123.45.67.89

-c “set volume [\”Engineering_1\” \”Engineering_2\”]

cacheReadPrefetch=TRUE;”
Setting the
Modification Priority
Modification priority defines how much processing time is allocated for volume
modification operations. Time allocated for volume modification operations affects
system performance. Increases in volume modification priority can reduce read/write
performance. The modification priority affects these operations:

Copyback

Reconstruction

Initialization

Changing the segment size

Defragmentation of a volume group

Adding free capacity to a volume group

Changing the RAID level of a volume group
The lowest priority rate favors system performance, but the modification operation
takes longer. The highest priority rate favors the modification operation, but the
system performance might be degraded.
Use the
set volume
command to define the modification priority for a volume.
The command has this form: