iopattern - print disk I/O pattern. Uses DTrace. iopattern [-v] [-d device] [-f filename] [-m mount_point] [interval [count]] 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 the root user or users with the dtrace_kernel privilege can run this command. Solaris stable - needs the io provider.

-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 directory. The DTraceToolkit docs may include full worked examples with verbose 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)