


IOSTAT(1)	    UNIX Programmer's Manual		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) processes,
     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 deter-
     mine 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 displays 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)









Printed 11/26/99	 April 29, 1985                         1



