Viewing Cache Statistics
87
You can change the cache size, the cache page size values, or the type of
caching for any physical disk unit without affecting the information stored
on it. Follow these steps:
1.
Disable the cache:
raid5 -d
device
setcache 0
2.
Wait for the cache memory to be written to disk, which may take
several minutes.
3.
Reassign cache size and re-enable caching, for example, with a cache
size of 64 MB:
raid5 -d
device
setcache 1 -u 64 [parameters
Note:
Before changing a cache parameter, you must always disable cache.
Viewing Cache Statistics
If you use storage-system caching, you can use the raid5 getcache command
to get information on cache activity. The information in this command’s
output, particularly the percentage of cache hits, may help you decide on the
most efficient cache page size and whether a physical disk unit really
benefits from caching.
Note:
If a disk module in location A0, B0, C0, D0, or E0 fails, caching is
disabled until the failed module is replaced. If an SP fails, caching is disabled
until the failed SP is replaced.
To display cache information, use
raid5 -d
device
getcache
Following is a sample output:
Usable Cache: 8
Page size: 2
Cache State: Enabled
Low Watermark; 75
High Watermark: 90
SP A Cache Pages: 2048
SP B Cache Pages: 2047
Unassigned Cache Pages: 0
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