i
iostat(1) | iostat(1) |
NAME
iostat - report I/O statistics
SYNOPSIS
iostat
DESCRIPTION
iostat iteratively reports I/O statistics for each active disk on the system. Disk data is arranged in a
Column Heading | Interpretation |
device | Device name |
bps | Kilobytes transferred per second |
sps | Number of seeks per second |
msps | Milliseconds per average seek |
If two or more disks are present, data is presented on successive lines for each disk.
To compute this information, seeks, data transfer completions, and the number of words transferred are counted for each disk. Also, the state of each disk is examined HZ times per second (as de®ned in <sys/param.h >) and a tally is made if the disk is active. These numbers can be combined with the transfer rates of each device to determine average seek times for each device.
With the advent of new disk technologies, such as data striping, where a single data transfer is spread across several disks, the number of milliseconds per average seek becomes impossible to compute accu- rately. At best it is only an approximation, varying greatly, based on several dynamic system conditions. For this reason and to maintain backward compatibility, the milliseconds per average seek ( msps ) ®eld is set to the value 1.0.
Options
iostat recognizes the following options and
Report terminal statistics as well as disk statistics. Terminal statistics include: |
tin Number of characters read from terminals. tout Number of characters written to terminals.
us Percentage of time system (active processors) has spent in user mode.
ni Percentage of time system (active processors) has spent in user mode running
sy Percentage of time system (active processors) has spent in system mode. id Percentage of time system (active processors) has spent idling.
interval Display successive lines which are summaries of the last interval seconds. The ®rst line reported is for the time since a reboot and each subsequent line is for the last interval only.
count | Repeat the statistics count times. |
EXAMPLES
Show current I/O statistics for all disks:
iostat
Display I/O statistics for all disks every 10 seconds until INTERRUPT or QUIT is pressed:
iostat 10
Display I/O statistics for all disks every 10 seconds and terminate after 5 successive readings:
iostat 10 5
Display I/O statistics for all disks every 10 seconds, also show terminal and processor statistics, and terminate after 5 successive readings:
iostat
WARNINGS
Users of iostat must not rely on the exact ®eld widths and spacing of its output, as these will vary depending on the system, the release of
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