Mac Formatting Guide

Covers Disk Utility For: 10.11 — 10.12

Jump to a Topic
Jump to a Topic


This formatting guide focuses on the Disk Utility application for versions 10.11 and 10.12 of the Mac operating system. If you’re accustomed to using the Disk Utility in earlier versions of OS X, it will be worth reading through this document to get familiar with the changes to the user interface and formatting process.

Interface Changes

Compared to earlier versions, some features have moved to new locations, others have been removed entirely. One change is that many of the buttons that were once on the toolbar (like Verify, Burn, and New Image) have been removed. They have been replaced by a mix of the operating mode buttons (First Aid, Partition, and Erase) and the most common function buttons (Mount/Unmount is now a single, context-sensitive button, and Info).

Additionally when you select a disk or volume, the default view provides key drive statistics and a breakdown of the file types that are stored on your drive — the latter feature serves the same purpose as the storage screen shown for iOS devices when they are mounted in iTunes, allowing you to see which type of media are taking up the most space on your device (or in this case, your hard drive or SSD).

Terminology Updates

This version of Disk Utility refers to the physical drive connected to your computer (internally or externally) as a ‘physical disk.’ The disk space you create and work with is now referred to as a ‘physical volume’, even though technically the volume is a digital or ‘logical ‘ entity, not a physical one.

Step 1

Typically the easiest way to access the Disk Utility application is to use the Spotlight search tool built into your OS X Menubar.

Click the magnifying glass icon in the top-right corner of your screen. Type ‘Disk Utility’. The first search result should automatically highlight the application. Press the Return key or double-click the name to launch the application.

Step 2

Each physical disk connected to your Mac appears as an icon in the sidebar on the left. Similar to prior versions of Disk Utility, the volumes contained within that disk (i.e. the partitions you create) will be indented beneath the physical disk’s icon.

To create a single OS X Extended (Journaled) volume on your disk you need to first highlight the physical disk.

Note: If you’re using a new, external drive from OWC for the first time, notice the physical disk has a volume associated with it called “OWC Setup”. If you are using Disk Utility to format the drive and you don’t need the bundled software (or prefer to access it from your online account), you can ignore this default volume.

If you would like to potentially keep the share ware on the drive and use the OWC Drive Guide to format your disk, please quit Disk Utility and click here for details.

Step 3

Unlike prior versions of Disk Utility, if your physical disk has not already been formatted for OS X, you cannot add a new partition until you use the Erase function to format the drive for the first time.

Click the Erase button on the toolbar. This will reveal a new interface. Instead of the main window displaying features of the Erase mode, a “sheet” drops down from the toolbar.

Step 4

First give your new physical volume a name. It is still recommended that you only use letters, numbers, dashes, and underscores in the name. Avoid using special characters and slashes.

If you intend to use this volume only with OS X, leave the default Format setting of ‘OS X Extended (Journaled)’ intact. If you want your volume to be readable on both Mac and PC (at the expense of some performance), choose ExFAT.

Note that the physical disk’s partition map scheme (listed as ‘Scheme’ in the screenshot at right) is now part of the ‘Erase’ process, rather than the partition process. This too should remain at the default setting (‘GUID Partition Map’), even if you’re using ExFAT as the format.

When you’re ready, click the Erase button on the sheet.

Step 5

Once you’ve clicked the Erase button, the first sheet will close and a new sheet with status information will appear in its place (click “Show Details” to reveal more information, as seen at below).

It may take a minute or two for the drive to be formatted and initialized. Once the process is complete, you should see a new physical volume with the name you chose in Step 4, indented beneath the name of the physical disk. Click Done when you are ready.

If you do not need to create additional partitions on your physical disk, you can quit Disk utility at this stage and begin using your newly formatted drive.

Time Machine Notes:

If Time Machine is active on your computer when you walk through the Disk Utility process, a message will appear when the volume has been created, asking you if you want to use it as a Time Machine backup. Unless you set the drive up for that specific reason, click ‘Don’t Use.’

If you did intend to set up a Time Machine Disk, but you’re not storing sensitive information, it is a good idea to leave ‘Encrypt Backup Disk’ unchecked. This may aid in the recovery of data should something happen to your physical disk down the road. All drives will eventually fail, regardless of make or model.

Optional: Creating Additional Partitions

Step 6a

If you want to add additional partitions to your physical disk so that you can store different types of information in logically separated volumes (i.e. each with its own name, etc.), highlight the physical disk icon again and click the ‘Partition’ button.

This will open another sheet from the toolbar with a set of buttons and visual aids to assist you in setting up the partitions.

Step 6b

At first, the pie chart will show a solid blue circle — this represents the volume you just created (as seen in the previous step). The entire physical disk is dedicated to this one volume for the time being.

Click the ‘+’ button underneath the pie chart to begin the repartition process.

By default this will split the disk in half (shown below), producing a new untitled volume, while maintaining the original volume at half its original size.

Step 6c

Next to the Partition field, change the name from Untitled to whatever you would like to use. The same guidelines used in Step 4 apply here as well.

Step 6d

Decide whether you want to maintain the default 50/50 split of the device’s capacity, or if you would like one partition to be larger than the other. If so, grab one of the circular handles and drag to re-apportion the pie to the different drives (example shown below).

Important: the selected partition’s name will always appear next to ‘Partition’ and the blue segment of the pie always belongs to that same selected partition. You can click the white portion of the pie graphic to select and modify the other partition.

In this case, “Vacation Videos” will occupy 1.5TB of the total 2TB space available on the physical disk. As noted previously, you can leave the format at its default if the new partition is strictly for use with Macs, or choose ExFAT if the partition needs to be accessible to both Macs and PCs.

Step 7

Add more partitions if necessary (using the same process described in Step 6b-6d), or if not, click Apply.

You will again see the original sheet disappear and a new one take its place, this time with partition status information. The process may take a minute or two depending on the setup you specified.

Click Done when the process has finished.

Once complete you should see both of physical volumes indented beneath the physical disk icon, and they will be color-coded in the interface as well (example shown below).

Both volumes should mount on your Desktop as well, assuming your Finder Preferences are set to allow that. At this point the new volumes are ready to be used and you can quit the Disk Utility application.

Free Support Chat

Our free award-winning support team is ready to answer all of your questions. Technical support is available Monday - Friday: 9AM - 6PM. Customer Support & Sales is available Monday - Friday: 8AM - 8PM. Support is unavailable on U.S. Federal holidays. Talk to a human today.