Use the iostat command to report statistics about disk input and output, and to produce measures of throughput, utilization, queue lengths, transaction rates, and service time. For a detailed description of this command, refer to the iostat ( 1M ) man page.
How to Display Disk Utilization Information (iostat)
You can display disk utilization information by using the iostat command with a time interval in seconds.
$ iostat 5
tty fd0 sd3 nfs1 nfs31 cpu
tin tout kps tps serv kps tps serv kps tps serv kps tps serv us sy wt id
0 1 0 0 410 3 0 29 0 0 9 3 0 47 4 2 0 94
The first line of output shows the statistics since the last time the
system was booted. Each subsequent line shows the interval statistics. The
default is to show statistics for the terminal (tty), disks
(fd and sd), and CPU (cpu).
Example 20.3. Displaying Disk Utilization Information
The following example shows disk statistics that were gathered every five seconds.
$ iostat 5
tty sd0 sd6 nfs1 nfs49 cpu
tin tout kps tps serv kps tps serv kps tps serv kps tps serv us sy wt id
0 0 1 0 49 0 0 0 0 0 0 0 0 15 0 0 0 100
0 47 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 44 6 132 0 0 0 0 0 0 0 0 0 0 0 1 99
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 3 1 23 0 0 0 0 0 0 0 0 0 0 0 1 99
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100
The following table describes the fields in the output of the iostat n
command.
|
Device Type |
Field Name |
Description |
|---|---|---|
|
Terminal |
Device Type | |
|
|
Number of characters in the terminal input queue | |
|
|
Number of characters in the terminal output queue | |
|
Disk |
Device Type | |
|
|
Blocks per second | |
|
|
Transactions per second | |
|
|
Average service time, in milliseconds | |
|
CPU |
Device Type | |
|
|
In user mode | |
|
|
In system mode | |
|
|
Waiting for I/O | |
|
|
Idle |
How to Display Extended Disk Statistics (iostat -xtc)
Run the iostat -xtc command to display extended disk statistics.
$ iostat -xtc
extended device statistics tty cpu
device r/s w/s kr/s kw/s wait actv svc_t %w %b tin tout us sy wt id
fd0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 0 0 0 0 0 100
sd0 0.0 0.0 0.4 0.4 0.0 0.0 49.5 0 0
sd6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
nfs1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
nfs49 0.0 0.0 0.0 0.0 0.0 0.0 15.1 0 0
nfs53 0.0 0.0 0.4 0.0 0.0 0.0 24.5 0 0
nfs54 0.0 0.0 0.0 0.0 0.0 0.0 6.3 0 0
nfs55 0.0 0.0 0.0 0.0 0.0 0.0 4.9 0 0
The iostat -xtc command displays a line of output for each disk. The output fields are described in the following list.
r/s
Reads per second
w/s
Writes per second
kr/s
Kbytes read per second
kw/s
Kbytes written per second
wait
Average number of transactions that are waiting for service (queue length)
actv
Average number of transactions that are actively being serviced
svc_t
Average service time, in milliseconds
%w
Percentage of time that the queue is not empty
%b
Percentage of time that the disk is busy