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Chapter 7: Caching
Setting Cache Parameters
The cache parameters you specify for the entire storage system are the cache
size of 8 or 64 MB, depending on the amount of memory the SPs have, and
the cache page size, as 2, 4, 8, or 16 KB.
To set up caching, use the raid5 setcache command:
raid5 -d
device
setcache
enable
|
disable
[-u
usable
] [-p
page
] [-l
low
] [-h
high
]
In this syntax, variables mean:
enable | disable Enter 1 to enable caching or 0 to disable caching.
-u usable
Size in megabytes to use for caching, not greater than the SP
memory size as displayed by raid5 getagent (see “Getting
Device Names With getagent,” in Chapter 3). Valid values
are 0, 8, and 64:
•
0: user has selected to disable the cache
•
other values: user has selected to enable the cache
The command line interface does not let you specify more
memory than you have. If you specify less than you have,
the remaining memory is unused.
Note:
For caching, both SPs must have the same amount of
cache memory in order for caching to be preserved in the
event of shutdown or other power loss.
-p page
Size in KB of pages into which to partition the cache. Valid
sizes are 2, 4, 8, and 16. The default is 2, regardless of
whether caching is enabled or disabled.
-l low
Percentage of cache full that discontinues flushing. Valid
values are 0 through 100; the default is 50, regardless of
whether caching is enabled or disabled.
-h high
Percentage of cache full that initiates flushing. Valid values
are 0 through 100; the setting must be greater than the low
watermark. The default is 75, regardless of whether caching
is enabled or disabled.
This command has no output.
