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)