Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

If an application is doing sequential I/O to large files, it should issue requests
larger than the discovered_direct_iosz. This causes the I/O requests to be
performed as discovered direct I/O requests, which are unbuffered like direct I/O
but do not require synchronous inode updates when extending the file. If the file
is too large to fit in the cache, then using unbuffered I/O avoids throwing useful
data out of the cache and lessons CPU overhead.
About obtaining file I/O statistics using the Quick I/O interface
The qiostatcommand provides access to activity information on Quick I/O files
on VxFS file systems. The command reports statistics on the activity levels of
files from the time the files are first opened using their Quick I/O interface. The
accumulated qiostat statistics are reset once the last open reference to the Quick
I/O file is closed.
The qiostat command displays the following I/O statistics:
■ Number of read and write operations
■ Number of data blocks (sectors) transferred
■ Average time spent on read and write operations
When Cached Quick I/O is used, qiostat also displays the caching statistics when
the -l (the long format) option is selected.
The following is an example of qiostat output:
OPERATIONS FILE BLOCKS AVG TIME(ms)
FILENAME READ WRITE READ WRITE READ WRITE
/db01/file1 0 00 0 0.0 0.0
/db01/file2 0 00 0 0.0 0.0
/db01/file3 73017 181735 718528 1114227 26.8 27.9
/db01/file4 13197 20252 105569 162009 25.8 397.0
/db01/file5 0 00 0 0.0 0.0
For detailed information on available options, see the qiostat(1M) manual page.
About I/O statistics data
Once you gather the file I/O performance data, you can use it to adjust the system
configuration to make the most efficient use of system resources.
Tuning for performance
About tuning VxFS
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