man : iostat(8)
IOSTAT(8) OpenBSD System Manager's Manual IOSTAT(8)
iostat - report I/O statistics
iostat [-CDdIT] [-c count] [-M core] [-N system] [-w wait] [drives]
iostat displays kernel I/O statistics on terminal, disk and CPU
operations. By default, iostat displays one line of statistics averaged
over the machine's run time. The -I option causes iostat to print raw,
The options are as follows:
-C Show CPU statistics. This is enabled by default unless the -D,
-d, or -T flags are used.
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.
Unless overridden by the -w option, the wait interval between
lines is 1 second.
-D Show alternate disk statistics. Displays kilobytes transferred,
number of transfers, and time spent in transfers. Use of this
flag disables the default display.
-d Show disk statistics. This is the default. Displays kilobytes
per transfer, number of transfers, and megabytes transferred.
Use of this flag disables display of CPU and tty statistics.
-I Show the running total values, rather than an average.
Extract values associated with the name list from the specified
core instead of the default /dev/mem.
Extract the name list from the specified system instead of the
-T Show tty statistics. This is enabled by default unless the -C,
-D, or -d flags are used.
Pause wait seconds between each display. Unless a count is
specified via the -c option, iostat will display output until it
iostat displays its information in the following format:
tin characters read from terminals
tout characters written to terminals
Disk operations. The header of the field is the disk name and unit
number. If more than four disk drives are configured in the
system, iostat displays only the first four drives. To force
iostat to display specific drives, their names may be supplied on
the command line.
KB/t Kilobytes transferred per disk transfer
t/s Transfers per second
MB/s Megabytes transferred per second
The alternate display format, (selected with -D), presents the
KB Kilobytes transferred
xfr Disk transfers
time Seconds spent in disk activity
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 processing interrupts
id % of CPU time in idle mode
/bsd default kernel namelist
/dev/mem default memory file
fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), top(1), pstat(8),
The sections starting with ``Interpreting system activity'' in Installing
and Operating 4.3BSD.
OpenBSD 4.9 February 10, 2011 OpenBSD 4.9