IOSTAT(1)                                                            IOSTAT(1)



NAME
       iostat - report I/O statistics

SYNOPSIS
       iostat [ drives ] [ interval [ count ] ]

DESCRIPTION
       _I_o_s_t_a_t iteratively reports the number of characters read and written to
       terminals per second, and, for each disk, the number of  transfers  per
       second,  kilobytes  transferred  per  second,  and the milliseconds per
       average seek.  It also gives the percentage  of  time  the  system  has
       spent  in  user  mode,  in  user mode running low priority (niced) pro‐
       cesses, in system mode, and idling.

       To compute this information, for each disk,  seeks  and  data  transfer
       completions  and number of words transferred are counted; for terminals
       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.  From these  numbers  and  given
       the  transfer  rates of the devices it is possible to determine average
       seek times for each device.

       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.

       If more than 4 disk drives are configured in the  system,  _i_o_s_t_a_t  dis‐
       plays  only  the  first  4  drives, with priority given to Massbus disk
       drives (i.e. if both Unibus and Massbus  drives  are  present  and  the
       total  number  of  drives  exceeds 4, then some number of Unibus drives
       will not be displayed in favor of the Massbus drives).  To force _i_o_s_t_a_t
       to  display specific drives, their names may be supplied on the command
       line.

FILES
       /dev/kmem
       /vmunix

SEE ALSO
       vmstat(1)



4th Berkeley Distribution       April 29, 1985                       IOSTAT(1)