NAME

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

SYNOPSIS

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

DESCRIPTION

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 command.

OPTIONS

-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

EXAMPLES

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 /

FIELDS

%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

IDEA

Ryan Matteson

DOCUMENTATION

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

EXIT

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

AUTHOR

Brendan Gregg [Sydney, Australia]