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.