Displaying Disk Utilization Information (iostat)

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)

1. 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 13–3 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.

How to Display Extended Disk Statistics (iostat -xtc)

1. 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