How to use Disk Utility to partition Hard Disk / Solid State Disk Drive on Mac

Macintosh OSX Disk Utility


As Wikipedia Says: Disk Utility is a system utility for performing disk and disk volume-related tasks on the OS X operating system by Apple Inc.

Day to day functions supported by Disk Utility are:


  • Creation, conversion, backup, compression and encryption of logical volume images from a wide range of formats read by Disk Utility to .dmg or, for CD/DVD images, .cdr
  • Mounting, unmounting and ejecting external disk volumes
  • Enabling or disabling journaling
  • Verifying a disk’s integrity, and repairing it if the disk is damaged
  • Erasing, formatting, partitioning and cloning disks
  • Secure deletion of free space or disk using a “zero out” data, a 7-pass DOD 5220-22 M standard, or a 35-pass Gutmann algorithm
  • Adding or changing partition table between Apple Partition Table, GUID Partition Table and master boot record (MBR)
  • Restoring volumes from Apple Software Restore (ASR) images
  • Checking the S.M.A.R.T. status of a hard disk
  • Disk Utility functions may also be accessed from the OS X command line with the diskutil and hdiutil commands.

Now will learn how to partition disk,


Important Note:

  • Partitioning a disk erases all the data previously stored on it
  • By using partition feature of disk utility it divides disk into sections called ‘partitions’ which appear on the desktop as separate disks.


Precaution: Before moving forward backup all your computer data using Time Machine on different hard drive other than that you are currently partitioning.


Here is how to Partition a disk

Step 01: Connect External Disk to your Mac using USB / FireWire cable for purpose partitioning it

Step 02: Locate ‘Disk Utility App in Applications > Utilities

Step 03: Select the disk that you want to partition and click on Erase

Step 04: When erase disk popup will appear under ‘Name’ section give disk a name, Under Format section choose ‘OSX Extended (Journaled), Under ‘Scheme’ section choose ‘GUID Partition Map’ in dropdown.

01 Disk Utility Erase Disk on Macintosh OSX

Click on Done once Disk Utility finish erasing disk

Step 05: While disk that you want to partition is selected click on Partition.

Step 06: Tweak the number of partitions from the Volume Scheme pop-up menu. You can add remove & manage number of partition by using ‘+’ & ‘-’ sign

02 Disk Utility Partition Disk

03 Disk Utility Number of Partition Manage

Step 07: Click each partition and type a name for it, choose a format such as OS X Extended (Journaled) and then type a size. You can also drag the divider between the partitions to change their sizes. If a partition’s name has an asterisk beside it, it’s shown larger than its actual size in order to display its name clearly.

Step 08: As shown in below image you can choose various format such as ‘OS X Extended (Journaled, Encrypted)’ just to password protect your external disk. While partitioning disk using encrypted volume Disk Utility will ask to enter & set password for new external disk.

04 Disk Utility Partition Format

I hope this information helps you to successfully partition your new external disk drive,

Thanks & Regards
Mandar Apte

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