solaris - iostat (1)

     iostat - report I/O statistics

     /usr/bin/iostat [ -cdDItx ] [ -l n ] [ disk ...  ]
          [ interval [ count ] ]

     iostat iteratively reports terminal and disk  I/O  activity,
     as well as CPU utilization.  The first line of output is for
     all time since boot; each subsequent line is for  the  prior
     interval only.

     To compute this information, the kernel maintains  a  number
     of  counters.   For  each  disk,  the  kernel  counts reads,
     writes, bytes read, and  bytes  written.   The  kernel  also
     takes  hi-res  time  stamps  at queue entry and exit points,
     which allows it to keep track  of  the  residence  time  and
     cumulative  residence-length  product for each queue.  Using
     these values, iostat produces highly  accurate  measures  of
     throughput,  utilization,  queue  lengths, transaction rates
     and service time.  For terminals  collectively,  the  kernel
     simply counts the number of input and output characters.

     For more general system statistics, use sar(1), sar(1M),  or
     vmstat(1M).

     See Solaris 1.x to Solaris 2.x Transition Guide  for  device
     naming conventions for disks.

     iostat's activity class options default  to  tdc  (terminal,
     disk, and CPU). If any activity class options are specified,
     the default is completely overridden.  Therefore, if only -d
     is  specified,  neither  terminal nor CPU statistics will be
     reported.  The last disk option specified (-d, -D, or -x) is
     the only one that is used.

     -c         Report the percentage  of  time  the  system  has
               spent  in  user  mode, in system mode, waiting for
               I/O, and idling.

     -d         For each disk, report  the  number  of  kilobytes
               transferred  per  second,  the number of transfers
               per second, and the average service time  in  mil-
               liseconds.

     -D         For each  disk,  report  the  reads  per  second,
               writes  per  second,  and percentage disk utiliza-
               tion.


               rates (where applicable).

     -t         Report the number of characters read and  written
               to terminals per second.

     -x         For each disk, report extended  disk  statistics.
               The output is in tabular form.

     -l n       Limit the number of disks included in the  report
               to  n; the disk limit defaults to 4 for -d and -D,
               and unlimited for  - x.   Note:  disks  explicitly
               requested (see disk below) are not subject to this
               disk limit.

     disk      Explicitly specify the disks to  be  reported;  in
               addition  to  any explicit disks, any active disks
               up to the disk limit (see -l above) will  also  be
               reported.

     count     Only print count reports.

     interval  Report once each interval seconds.

     example% iostat -xtc 5 2
                            extended disk statistics       tty         cpu
     disk r/s  w/s Kr/s Kw/s wait actv svc_t  %w  %b  tin tout us sy wt id
     sd0   6.2 0.0 21.5  0.0 0.0  0.1  24.1   0   15   0   84  4  94  2 0
     sd1   1.8 0.0 14.3  0.0 0.0  0.1  41.6   0    7
     sd2   0.0 0.0  0.0  0.0 0.0  0.0   0.0   0    0
     sd3   5.6 0.2 25.7  0.2 0.0  0.1  22.5   0   13
                            extended disk statistics       tty         cpu
     disk r/s  w/s Kr/s Kw/s wait actv svc_t  %w  %b  tin tout us sy wt id
     sd0   2.6 3.0 20.7 22.7 0.1  0.2  59.2   6   19   0   84  3  85 11 0
     sd1   4.2 1.0 33.5  8.0 0.0  0.2  47.2   2   23
     sd2   0.0 0.0  0.0  0.0 0.0  0.0   0.0   0    0
     sd3  10.2 1.6 51.4 12.8 0.1  0.3  31.2   3   31
     example%

     The fields have the following meanings:

          disk    name of the disk
          r/s     reads per second
          w/s     writes per second
          Kr/s    kilobytes read per second
          Kw/s    kilobytes written per second
          wait    average number of transactions waiting for ser-
                  vice (queue length)
          actv    average number of transactions  actively  being
                  serviced  (removed  from  the queue but not yet
                  completed)

          %w      percent of time there are transactions  waiting
                  for service (queue non-empty)
          %b      percent of time the disk is busy  (transactions
                  in progress)

     sar(1), sar(1M), vmstat(1M)

     System Administration Guide, Volume II