Partition a Drive with OS X El Capitan's Disk Utility

OS X El Capitan brought a makeover to Disk Utility, the all-purpose app for managing Mac’s drives. While it retains most of its key features, including the ability to partition a drive into multiple volumes, it has changed the process a bit.

If you’re an old hand at working with your Mac’s storage devices, then this should be pretty simple; just a few changes in names or locations of Disk Utility features. If you’re new to the Mac, this guide will be an excellent walk-through of how to create multiple partitions on a storage device.

In this guide, we'll concentrate on the basics of creating drive partitions. If you need to resize, add, or delete existing partitions, you'll find detailed instructions in our How to Resize a Mac Volume (OS X El Capitan or Later) guide.

What You Need

• A Mac with OS X 10.11 (El Capitan) or later.
• One or more storage devices that you wish to partition.
• A few minutes of your time. The partitioning process is relatively quick; you may find that you spent more time reading this guide than it took to actually partition your drive.

Nevertheless, it’s a good idea to read through all the steps of the guide at least once before starting the partitioning process.

Proceed to Page 2

The version of Disk Utility that's included with OS X El Capitan and later allows you to divide a storage device into multiple partitions. Once the partition process is complete, each partition becomes a mountable volume your Mac can use in any way you see fit.

Each partition can use one of six format types, four of which are exclusively for OS X file systems, and two that can be used by PCs.

Partitioning can be used to divide nearly any type of storage device, including SSDs, hard drives, and USB flash drives; just about any storage device that you can use with the Mac can be partitioned.

In this guide, we're going to divide a drive into two partitions. You can use the same process to create any number of partitions; we just stopped at two because that's all you need to understand the basic process.

Partition a Drive

1. If the drive that you wish to partition is an external drive, be sure it's connected to your Mac and powered on.
2. Launch Disk Utility, located at /Applications/Utilities/.
3. Disk Utility will open in a single window divided into two panes, with a toolbar across the top.
4. The left-hand pane contains the drive(s) and any volumes associated with the drives in a hierarchical view. In addition, the left-hand pane further divides the available storage devices into types, such as Internal and External.
5. Select the storage device you wish to partition from the left-hand pane. You can only partition the drive, not any of the associated volumes. Drives usually have names that refer to the drive manufacturer or an external enclosure manufacturer. In the case of a Mac with a Fusion drive, it may simply be named Macintosh HD. To make things a bit confusing, both the drive and a volume can have the same name, so pay attention to the hierarchy displayed in the left-hand pane and only select the storage device at the top of a hierarchical group.
6. The selected drive will appear in the right-hand pane with details about it, such as location, how it’s connected, and the partition map in use. In addition, you'll see a long bar that represents how the drive is currently divided up. Chances are it will appear as one long bar if there's only a single volume associated with it.
7. With the drive selected, click the Partition button in Disk Utility's Toolbar.
8. A sheet will drop down, displaying a pie chart of how the drive is currently divided up. The sheet also shows the currently selected partition name, format type, and size. Assuming this is a new drive ​or one you just formatted, the pie chart likely shows a single volume.

To learn how to add volumes, go on to Page 3.

So far, you've selected a drive to partition, and brought up the partitioning pie chart, which displays the current volumes as pie slices.

Warning: Partitioning your drive can result in data loss. If the drive you're partitioning contains any data, be sure to back up the information before proceeding.

Add an Additional Volume

1. To add another volume, click the plus (+) button just below the pie chart.
2. Clicking the plus (+) button again will add an additional volume, each time dividing the pie chart into equal shares. Once you have the number of volumes you wish, it's time to adjust their sizes, give them names, and select a format type to use.
3. When working on the pie chart, it's best to start with the first volume, which is at the top of the chart, and work your way around in a clockwise fashion.
4. Select the first volume by clicking within the volume space in the pie chart.
5. In the Partition field, enter a name for the volume. This will be the name that displays on your Mac’s desktop.
6. Use the dropdown Format menu to select a format to use on this volume. The choices are:
   • OS X Extended (Journaled): The default, and most often used the file system on the Mac.
   • OS X Extended (Case-sensitive, Journaled)
   • OS X Extended (Journaled, Encrypted)
   • OS X Extended (Case-sensitive, Journaled, Encrypted)
   • MS-DOS (FAT)
   • ExFat
7. Make your selection.

Adjusting Volume Size

1. You can adjust volume size by either entering a volume size in the text box or by grabbing the pie slice anchor and dragging it to change the slice's size.
2. The latter method for changing the size works nicely until you get to the last pie slice. If you enter a size that is less than the remaining space, or you drag the pie slice anchor at the top of the pie chart, you'll create an additional volume.
3. If you create an additional volume by accident, you can remove it by selecting it and clicking the minus (-) button.
4. Once you've named all the volumes, assigned a format type, and verified that they're the sizes you need, click the Apply button.
5. The pie chart sheet will disappear and be replaced by a new sheet showing the status of the action. This should usually be Operation Successful.
6. Click the Done button.

That’s the scoop on using Disk Utility to partition your drive into multiple volumes. The process is fairly straightforward, but although the pie chart representation of the drive being partitioned into multiple volumes is helpful visually, it’s not that great a tool for actually dividing the space up, and can easily lead to extra steps, and the need to remove unwanted volumes that were accidentally created.