By default, the Tivoli® Storage
Manager server reads
and writes storage pool data with non-buffered I/O, which bypasses
the file system cache. Using file system cache can be beneficial in
certain situations but it is not a best practice.
About this task
If you switch to file system cache, change the default
with care. The use of file system cache can decrease overall server
throughput and increase server processor usage. Use file system cache
for storage pool I/O only if it results in a significant performance
improvement.
You might see benefits from using file system cache
in the following environments:
- A disk storage system that you are using for storage pools has
a relatively small cache memory size.
- The disk storage system does not provide read-ahead capability.
You must improve storage pool migration throughput from the disk volumes
by using the operating system read-ahead capability.
- Data that is stored on the Tivoli Storage
Manager server is
expected to be immediately retrieved through some other process.
Note: Enabling the server to use file system
cache is not a preferred practice. If you contact IBM® Software Support for a performance issue,
you must disclose that you are using this option. You might be asked
to disable this option before IBM can
resolve the issue.
Procedure
To use file system cache for storage pool I/O, complete
the following steps:
- Specify DIRECTIO NO in the dsmserv.opt file.
- Restart the server.
- Observe operations for the effects of the change and determine
whether to keep the DIRECTIO NO entry in the options
file or remove it.
Tip: To display the current
value for the DIRECTIO option, specify the option
name when you issue the QUERY OPTION command.