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


ziostat [-hIMrzZ] [interval [count]]


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.


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


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



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


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


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


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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