iosnoop(1m)                       USER COMMANDS                      iosnoop(1m)

       iosnoop - snoop I/O events as they occur. Uses DTrace.

       iosnoop [-a|-A|-Deghinostv] [-d device] [-f filename] [-m mount_point]
       [-n name] [-p PID]

       iosnoop prints I/O events as they happen, with useful details such as
       UID, PID, block number, size, filename, etc.

       This is useful to determine the process responsible for using the disks,
       as well as details on what activity the process is requesting. Behaviour
       such as random or sequential I/O can be observed by reading the block

       Since this uses DTrace, only users with root privileges can run this

       -a     print all data

       -A     dump all data, space delimited

       -D     print time delta, us (elapsed)

       -e     print device name

       -i     print device instance

       -N     print major and minor numbers

       -o     print disk delta time, us

       -s     print start time, us

       -t     print completion time, us

       -v     print completion time, string

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

       -f filename
              full pathname of file to snoop

       -m mount_point
              mountpoint for filesystem to snoop

       -n name
              process name

       -p PID process ID

       Default output, print I/O activity as it occurs,
              # iosnoop

       Print human readable timestamps,
              # iosnoop -v

       Print major and minor numbers,
              # iosnoop -N

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

       UID    User ID

       PID    Process ID

       PPID   Parent Process ID

       COMM   command name for the process

       ARGS   argument listing for the process

       SIZE   size of the operation, bytes

       BLOCK  disk block for the operation (location. relative to this
              filesystem.  more useful with the -N option to print major and
              minor numbers)

       STIME  timestamp for the disk request, us

       TIME   timestamp for the disk completion, us

       DELTA  elapsed time from request to completion, us (this is the elapsed
              time from the disk request (strategy) to the disk completion

       DTIME  time 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)

              timestamp for the disk completion, string

       DEVICE device name

       INS    device instance number

       D      direction, Read or Write

       MOUNT  mount point

       FILE   filename (basename) for I/O operation

       When filtering on PID or process name, be aware that poor disk event
       times may be due to events that have been filtered away, for example
       another process that may be seeking the disk heads elsewhere.

       See the DTraceToolkit for further documentation under the Docs directory.
       The DTraceToolkit docs may include full worked examples with verbose
       descriptions explaining the output.

       iosnoop will run forever until Ctrl-C is hit.

       Brendan Gregg [Sydney, Australia]

       iotop(1M), dtrace(1M)

version 1.50                      July 25, 2005                      iosnoop(1m)