qiostat

NAME

qiostat - VxFS Quick I/O for Databases statistics utility

SYNOPSIS

AVAILABILITY

VRTSvxfs

DESCRIPTION

qiostat prints and resets statistics on one or more VERITAS Quick I/O for Databases device files.

qiostat reads statistics for the specified Quick I/O files and prints them to standard output. These statistics show I/O activity since the last time the file was opened from the Quick I/O interface, and are valid as long as the file remains open. Statistics reset to zero when the last file open from the Quick I/O interface is closed.

CLUSTER FILE SYSTEM ISSUES

Quick I/O works on VxFS cluster file systems, but Cached Quick I/O is not currently supported.

OPTIONS

-c "count"

Stops after printing statistics count times.

-i "interval"

Prints updated I/O statistics every interval seconds. The first set of statistics reported are the totals since the last reset. Subsequent displays show the changes since the last report.

-l

Prints the statistics in long format. Also prints the caching statistics when Cached Quick I/O is enabled.

-o local

For a cluster Quick I/O file, the default behavior of qiostat is to display the sum of the statistics from all the cluster nodes where the file is opened through the Quick I/O interface. When the -o local option is specified, only the local node statistics are displayed. Similarly, if used with the -r option, only the local node statistics are reset.

-r

Resets statistics instead of printing them. This follows the same selection rules as printing for any device file. If interval is also specified, the first set of statistics are not printed because they were already reset to zero; subsequent activity prints statistics as usual.

OUTPUT FORMAT

Summary statistics for each object are printed in single line output records, preceded by two header lines. The output line consists of blank-separated fields for the file name, and statistics on read and write operations:

• number of read operations
• number of write operations
• number of blocks read
• number of blocks written
• average time spent on read operations in the interval
• average time spent on write operations in the interval

If the -i interval option is supplied, statistics are prefaced with a time stamp showing the current local time on the system.

If the -l option is specified, statistics are printed in two lines per object:

The first line is the same as described above. The second line shows the caching statistics. Cached Quick I/O performs buffered reads and returns cached data (if available) without doing reads from the disk. Writes are performed as modified direct writes, that is, after the direct write to disk is scheduled, the file system updates the copy of data in cache (if it exists) with the same data being written to disk. In the column headings of the second line:

• CREAD is the number of reads issued to cache
• PREAD is the number of reads to the disk required because the data was not available in cache
• HIT RATIO is the percentage of the read requests that did not have to perform physical I/O and were satisfied from the cache (CREADs - PREADs / CREADs = HIT RATIO)

EXIT CODES

qiostat exits with a non-zero status if the attempted operation fails. A non-zero exit code is not a complete indicator of the problems encountered, but rather denotes the first condition that prevented further execution of the command.

EXAMPLES

Display statistics for all device files on the file system /mnt/oracle:

qiostat /mnt/oracle/* 

Display five sets of I/O statistics at 10 second intervals:

qiostat -i 10 -c 5 /mnt/oracle/* 

Print cache statistics:

qiostat -l /mnt/oracle/* 

SEE ALSO

qioadmin (1), qiomkfile (1)