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iopattern(1)                    USER COMMANDS                   iopattern(1)


       iopattern - print disk I/O pattern. Uses DTrace.


       iopattern  [-v]  [-d  device]  [-f filename] [-m mount_point] [interval


       This prints details on the I/O access pattern for the  disks,  such  as
       percentage  of  events  that were of a random or sequential nature.  By
       default totals for all disks are printed.

       An event is considered random when the heads seek. This program  prints
       the  percentage  of events that are random. The size of the seek is not
       measured - it's either random or not.

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


       -v     print timestamp, 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


       Default output, print I/O summary every 1 second,
              # iopattern

       Print 10 second samples,
              # iopattern 10

       Print 12 x 5 second samples,
              # iopattern 5 12

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


       %RAN   percentage of events of a random nature

       %SEQ   percentage of events of a sequential nature

       COUNT  number of I/O events

       MIN    minimum I/O event size

       MAX    maximum I/O event size

       AVG    average I/O event size

       KR     total kilobytes read during sample

       KW     total kilobytes written during sample

       DEVICE device name

       MOUNT  mount point

       FILE   filename (basename) for I/O operation

       TIME   timestamp, string


       Ryan Matteson


       See  the  DTraceToolkit for further documentation under the Docs direc-
       tory. The DTraceToolkit docs may include full worked examples with ver-
       bose descriptions explaining the output.


       iopattern  will run forever until Ctrl-C is hit, or the specified count
       is reached.


       Brendan Gregg [Sydney, Australia]


       iosnoop(1M), iotop(1M), dtrace(1M)

version 0.70                     Jul 25, 2005                    iopattern(1)

Mac OS X 10.6 - Generated Thu Sep 17 20:07:55 CDT 2009
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