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ziostat(1M) -- Report ZFS read I/O activity

SYNOPSIS

ziostat [-hIMrzZ] [interval [count]]

DESCRIPTION

The ziostat utility reports a summary of ZFS read I/O operations. It first prints all activity since boot, then reports activity over a specified interval.

When run from a non-global zone (NGZ), only activity from that NGZ can be observed. When run from a the global zone (GZ), activity from the GZ and all other NGZs can be observed.

This tool is useful for determining if disk I/O is a source of application latency. Combined with vfsstat(1M), ziostat(1M) shows the relative contribution of disk I/O latency to overall I/O (and therefore application) latency.

OUTPUT

The ziostat utility reports the following information:

r/s	reads per second

kr/s	kilobytes read per second

actv	average number of ZFS read I/O operations being
		handled by the disk

wsvc_t	average wait time per I/O, in milliseconds

asvc_t	average disk service time per I/O, in milliseconds

%b	percent of time there is  an I/O operation pending

OPTIONS

The following options are supported:

-h Show help message and exit

-I Print results per interval, rather than per second (where applicable)

-M Print results in MB/s instead of KB/s

-r Show results in a comma-separated format

-z Hide zones with no read I/O activity

-Z Print results for all zones, not just the current zone

OPERANDS

interval

Specifies the length in seconds to pause between each interval report. If not specified, ziostat will print a summary since boot and exit.

count

Specifies the number of intervals to report. Defaults to unlimited if not specified.

SEE ALSO

iostat(1M), vfsstat(1M), mpstat(1M)

NOTES

This utility does not show any ZFS write I/O activity. Most write operations are asynchronous, so the latency of those operations committing to disk is much less important that read latency.

The output format from ziostat may change over time; use the comma-separated output for a stable output format.

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