Displaying Disk Utilization Information (iostat n)
Use the iostat command to report statistics about
disk input and output, and produces measures of throughput, utilization, queue
lengths, transaction rates, and service time. For a detailed description of
this command, refer to iostat(1M).
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).
The following table describes the fields in the iostat
command output.
Table 24–4 Output From the
iostat n
Command
|
Device Type
|
Field Name
|
Description
|
|
Terminal
|
|
|
|
|
tin
|
Number of characters in the terminal input queue
|
|
|
tout
|
Number of characters in the terminal output queue
|
|
Disk
|
|
|
|
|
bps
|
Blocks per second
|
|
|
tps
|
Transactions per second
|
|
|
serv
|
Average service time, in milliseconds
|
|
CPU
|
|
|
|
|
us
|
In user mode
|
|
|
sy
|
In system mode
|
|
|
wt
|
Waiting for I/O
|
|
|
id
|
Idle
|
Example—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
|
How to Display Extended Disk Statistics (iostat -xtc)
Run the iostat -xtc command to get 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 table.
Table 24–5 Output From the
iostat -xtc Command
|
Field Name
|
Description
|
|
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
|
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