iostat(1M)




NAME

     iostat - report I/O statistics


SYNOPSIS

     /usr/bin/iostat [-cCdDeEiImMnpPrstxXz] [-l n]  [-T  u  |  d]
     [disk...] [ interval [count]]


DESCRIPTION

     The iostat utility iteratively reports terminal,  disk,  and
     tape  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.

     During execution of this kernel status command, the  "state"
     of  the  kernel  can  change. An example would be CPUs going
     online or offline. iostat reports this as one or more of the
     following messages:

     device_name added
     device_name removed
     NFS_filesystem mounted
     NFS_filesystem unmounted
     cpu[s] taken offline: cpuid
     cpu[s] brought online: cpuid

     where device_name, NFS_filesystem  and  cpuid  are  replaced
     with  the  actual  name  or  names of the entities formatted
     according to other options.

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


OPTIONS

     The iostat utility'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.

     The following options are supported:

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

     -C    When the -n and -x options are also  selected,  report
           extended disk statistics aggregated by controller id.

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

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

     -e    Display device error  summary  statistics.  The  total
           errors, hard errors, soft errors, and transport errors
           are displayed.

     -E    Display all device error statistics.

     -i    In -E output, display the "Device Id" instead  of  the
           "Serial  No".  The  "Device Id" is a unique identifier
           registered by a driver through ddi_devid_register(9F).

     -I    Report the counts in each interval, rather than  rates
           (where applicable).

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

     -m    Report file system mount points. This option  is  most
           useful if the -P or -p option is also specified.

     -M    Display data throughput in MB/sec instead of KB/sec.

     -n    Display names  in  descriptive  format  (for  example,
           cXtYdZ, rmt/N, server:/export/path).

     -p    For each  disk,  report  per-partition  statistics  in
           addition to per-device statistics.

     -P    For each disk, report per-partition  statistics  only,
           no per-device statistics.

     -r    Display data in a comma-separated format.

     -s    Suppress messages related to "state changes."

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

     -T u | d
           Display a time stamp.

           Specify u for a printed representation of the internal
           representation  of  time.  See  time(2). Specify d for
           standard date format. See ctime(3C).

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

     -X    For disks under scsi_vhci control, also report statis-
           tics in  the form of target.controller.

     -z    Do not print lines whose underlying  data  values  are
           all zeros.


OPERANDS

     The following operands are supported:

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

     count Display only count reports.

     interval
           Report once each interval seconds.


EXAMPLES

     Example 1: Using the iostat command

     example% iostat -xtc 5 2

                       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
     sd0    0.4  0.3 10.4   8.0  0.0  0.0  36.9  0   1    0   10   0  0  1 99
     sd1    0.0  0.0  0.3   0.4  0.0  0.0  35.0  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
     nfs2   0.0  0.0  0.0   0.1  0.0  0.0  35.6  0   0
                 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
     sd0    0.0  0.0  0.0   0.0  0.0  0.0  0.0   0   0   0  155   0  0  0 100
     sd1    0.0  0.0  0.0   0.0  0.0  0.0  0.0   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
     nfs2   0.0  0.0  0.0   0.0  0.0  0.0  0.0   0   0

     device
           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  service
           (queue length)

     actv  average number of transactions actively being serviced
           (removed from the queue but not yet completed)

     svc_t average service time, in milliseconds

     %w    percent of time there  are  transactions  waiting  for
           service (queue non-empty)

     %b    percent of time the disk is busy (transactions in pro-
           gress)

     Example 2: Using the iostat command

     example% iostat -xnp

                     extended device statistics
     r/s  w/s  kr/s kw/s wait actv wsvc_t asvc_t %w %b device
     0.4  0.3  10.4  7.9  0.0  0.0    0.0   36.9  0  1 c0t0d0
     0.3  0.3   9.0  7.3  0.0  0.0    0.0   37.2  0  1 c0t0d0s0
     0.0  0.0   0.1  0.5  0.0  0.0    0.0   34.0  0  0 c0t0d0s1
     0.0  0.0   0.0  0.1  0.0  0.0    0.6   35.0  0  0 expositor:/export/home3/user3

     The fields have the same meanings as in the  previous  exam-
     ple, with the following additions:

     wsvc_t
           average service time in wait queue, in milliseconds

     asvc_t
           average service  time  active  transactions,  in  mil-
           liseconds


ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcsu                     |
    |_____________________________|_____________________________|


SEE ALSO

     sar(1),  sar(1M),  vmstat(1M),  time(2),  ctime(3C),  attri-
     butes(5), scsi_vhci(7D)

      System Administration Guide: Basic Administration


NOTES

     The sum of CPU utilization  might  vary  slightly  from  100
     because of rounding errors in the production of a percentage
     figure.


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