iotop - display top disk I/O events by process. Uses DTrace. iotop [-C] [-D|-o|-P] [-j|-Z] [-d device] [-f filename] [-m mount_point] [-t top] [interval [count]] iotop tracks disk I/O by process, and prints a summary report that is refreshed every interval. This is measuring disk events that have made it past system caches. Since this uses DTrace, only the root user or users with the dtrace_kernel privilege can run this command. Solaris stable - needs the io provider.

-C don't clear the screen

-D print delta times - elapsed, us

-j print project ID

-o print disk delta times, us

-P print %I/O (disk delta times)

-Z print zone ID

-d device instance name to snoop (eg, dad0)

-f filename full pathname of file to snoop

-m mount_point mountpoint for filesystem to snoop

-t top print top number only

Default output, print summary every 5 seconds # iotop

One second samples, # iotop 1

print %I/O (time based), # iotop -P

Snoop events on the root filesystem only, # iotop -m /

Print top 20 lines only, # iotop -t 20

Print 12 x 5 second samples, scrolling, # iotop -C 5 12

UID user ID

PID process ID

PPID parent process ID

PROJ project ID

ZONE zone ID

CMD command name for the process

DEVICE device name

MAJ device major number

MIN device minor number

D direction, Read or Write

BYTES total size of operations, bytes

ELAPSED total elapsed times from request to completion, us (this is the elapsed time from the disk request (strategy) to the disk completion (iodone))

DISKTIME total times for disk to complete request, us (this is the time for the disk to complete that event since it's last event (time between iodones), or, the time to the strategy if the disk had been idle)

%I/O percent disk I/O, based on time (DISKTIME)

load 1 minute load average

disk_r total disk read Kb for sample

disk_w total disk write Kb for sample

See the DTraceToolkit for further documentation under the Docs directory. The DTraceToolkit docs may include full worked examples with verbose descriptions explaining the output. iotop will run forever until Ctrl-C is hit, or the specified interval is reached. Brendan Gregg [Sydney, Australia] iosnoop(1M), dtrace(1M)