IOSTAT(8) NetBSD System Manager's Manual IOSTAT(8)
iostat -- report I/O statistics
iostat [-CdDITxy] [-c count] [-w wait] [drives]
iostat displays kernel I/O statistics on terminal, disk and CPU opera- tions. By default, iostat displays one line of statistics averaged over the machine's run time. The use of -c presents successive lines averaged over the wait period. The -I option causes iostat to print raw, unaver- aged values. Only the last disk option specified (-d, -D, or -x) is used. The options are as follows: -c count Repeat the display count times. Unless the -I flag is in effect, the first display is for the time since a reboot and each subsequent report is for the time period since the last display. If no wait interval is specified, the default is 1 second. -C Show CPU statistics. This is enabled by default unless the -d, -D, -T, or -x flags are used. -d Show disk statistics. This is the default. Displays kilo- bytes per transfer, number of transfers, and megabytes trans- ferred. Use of this flag disables display of CPU and tty statistics. -D Show alternative disk statistics. Displays kilobytes trans- ferred, number of transfers, and time spent in transfers. Use of this flag disables the default display. -I Show the running total values, rather than an average. -T Show tty statistics. This is enabled by default unless the -C, -d, or -D flags are used. -w wait Pause wait seconds between each display. If no repeat count is specified, the default is infinity. -x Show extended disk statistics. Each disk is displayed on a line of its own with all available statistics. This option overrides all other display options, and all disks are dis- played unless specific disks are provided as arguments. Additionally, separate read and write statistics are dis- played. -y Shows the extended statistics and additional queuing statis- tics. iostat displays its information in the following format: tty tin characters read from terminals tout characters written to terminals disks Disk operations. The header of the field is the disk name and unit number. If more drives are configured in the system that fit across the current display, iostat displays only those drives that fit on the display. To force iostat to display specific drives, they may be supplied on the command line, either as names or fnmatch() patterns. KB/t Kilobytes transferred per disk transfer t/s transfers per second MB/s Megabytes transferred per second The alternative display format, (selected with -D), presents the following values. KB Kilobytes transferred xfr Disk transfers time Seconds spent in disk activity With the -y flag, the following queuing measurements are added wait Number of I/O requests queued up actv Number of currently active I/O requests wsvc_t Average waiting time of an I/O request in milliseconds asvc_t Average duration of an I/O request in milliseconds wtime Seconds spent in the waiting queue. Queuing data might not be available from all drivers and is then shown as zeros. cpu us % of CPU time in user mode ni % of CPU time in user mode running niced processes sy % of CPU time in system mode in % of CPU time in interrupt mode id % of CPU time in idle mode
fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), vmstat(1), fnmatch(3), pstat(8) The sections starting with ``Interpreting system activity'' in Installing and Operating 4.3BSD.
iostat appeared in Version 6 AT&T UNIX. The -x option was added in NetBSD 1.4. Collection of queueing values and the -y option were added in NetBSD 8.0. NetBSD 9.0 July 29, 2018 NetBSD 9.0
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