iopattern(1m)

Usage

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

Overview

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.

Releases

115 releases since Mac OS X 10.5; the text changed 1 time.