---
name: "iopattern"
section: "1m"
platform: "macos"
package: "dtrace"
version: "413"
release: "macOS 26.5"
platforms: ["macos"]
url: "https://new.carta.tech/iopattern"
---

# iopattern(1m)

print disk I/O pattern. Uses DTrace.

## 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 \[Sydney, Australia\]

## SEE ALSO

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