IOSTAT(8)           UNIX Programmer's Manual            IOSTAT(8)

NAME
     iostat - report I/O statistics

SYNTAX
     iostat [ option ] ...  [ interval [ count ] ]

DESCRIPTION
     _I_o_s_t_a_t delves into the system and reports certain statistics
     kept about input-output activity.  Information is kept about
     different disks and about terminal ports.  For each disk,
     I/O completions and number of words transferred are counted;
     for terminal ports collectively, the number of input and
     output characters are counted.  Also, each sixtieth of a
     second, the state of each disk is examined and a tally is
     made if the disk is active.  The state of the system is also
     examined and placed in one of four categories, depending on
     whether the system is executing in user mode, in `nice'
     (background) user mode, in system mode, or idle.  From all
     these numbers and from the known transfer rates of the dev-
     ices it is possible to determine information such as the
     degree of I/O overlap and average seek times for each dev-
     ice.

     The optional _i_n_t_e_r_v_a_l argument causes _i_o_s_t_a_t to report once
     each _i_n_t_e_r_v_a_l seconds.  The first report is for  all time
     since a reboot and each subsequent report is for the last
     interval only.

     The optional _c_o_u_n_t argument restricts the number of reports.

     With no option argument _i_o_s_t_a_t reports the number of charac-
     ters of terminal I/O per second, for each disk the number of
     transfers per minute, the milliseconds per average seek, and
     the milliseconds per data transfer exclusive of seek time.
     It also gives the percentage of time the system has spend in
     each of the four categories mentioned above.

     The following options are available:

     -i   Report the percentage of time spent in each of the four
          categories mentioned above, the percentage of time
          spent in `I/O wait' (iowt: idle, but with a disk
          active), the percentage of time any disk was active
          (iact), and the percentage of time each disk was active
          (seeking, dks, or transferring, dkx).

     -o   Omit the headers and first line (data since boottime).

     -s   Report the raw timing information: 8 numbers indicating
          the percentage of time spent in each of the possible
          configurations of 4 system states with I/O active or
          not active, and a number of I/O states (2**n for n

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IOSTAT(8)           UNIX Programmer's Manual            IOSTAT(8)

          disks) reflecting the combinations of disks active at
          each sampling point.

     -b   Report on the usage of I/O buffers.

     -d   Print the date and time before each listing.

     -a   Print the actual time elapsed before each listing.

     -u   Report UNIBUS allocation statistics.

PROGRAM CONFIGURATION
     The iostat program must be modified for each hardware confi-
     guration for the disk monitoring to work correctly.  This
     must correspond to the way the kernel maintains the disk
     metering information.  There are NDISK (param.c) disks moni-
     tored, and the identity of each disk is determined by the
     definition of _X_X_DKN in the appropriate disk driver header
     file.  The disk with _X_X_DKN of 0 will appear first in the
     output listings, etc.  SMD-type disk drivers (hp, rp, rm)
     use one entry for each disk's seeks, from _X_X_DKN to _X_X_DKN +
     NDR - 1, with NDR drives.  The entry _X_X_DKN + NDR is used
     for the controller's transfers.  No other driver should be
     assigned a _X_X_DKN in this range.  Iostat expects that if
     there is an SMD driver, its _X_X_DKN will be 0.  In the iostat
     source, the defined constant LAST_DRV should be set to the
     entry number of the last slot used for drive seeks, e.g. 1
     for use with 2 hp drives, or -1 with no SMD drives.  Also,
     the transfer rates of each controller must be entered in the
     appropriate element of the array xf; this is used to deter-
     mine the transfer times printed.

FILES
     /unix
     /dev/kmem

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