How to Use Disk Utility in macOS

Disk Utility does it all

Disk Utility, a free application included with the Mac, is a multipurpose, easy-to-use tool for working with hard drives and drive images. Among other things, Disk Utility can erase, format, repair, and partition hard drives, as well as create RAID arrays. You can also use it to create a clone of any drive, including your startup drive.

The first five sections in this article cover using Disk Utility with macOS Catalina (10.15) through OS X El Capitan (10.11), while the rest cover using Disk Utility included with OS X Yosemite (10.10) through OS X Leopard (10.5).

Repair Your Mac's Drives With Disk Utility's First Aid

Disk Utility's First Aid

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Disk Utility's ability to repair disk issues underwent an overhaul with OS X El Capitan. The new Disk Utility app's First Aid feature can verify and repair drives connected to your Mac, but if your troubles are with the startup drive, you have to take a few extra steps.

Format a Mac's Drive Using Disk Utility

Disk Utility OS X El Capitan

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The version of Disk Utility that's included with OS X El Capitan and later versions of the Mac OS has been panned for removing capabilities and changing how certain features work.

However, when it comes to formatting a drive connected to your Mac, the basics remain the same.

Partition a Mac's Drive Using Disk Utility

Disk Utility Partition Pie Chart El Capitan

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Partitioning a drive into multiple volumes is still taken care of by Disk Utility, but there have been changes, including the use of a pie chart to visualize how a drive's partition table is divided up.

All in all, it's a useful visual, though different from the stacked column chart used in earlier versions of Disk Utility.

How to Resize a Mac Volume

Disk Utility Partitioning OS X El Capitan

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Resizing a volume without losing data is still possible using Disk Utility. However, the process has undergone a few changes that can leave many users scratching their heads.

Use Disk Utility to Clone a Mac's Drive

Disk Utility Restore process details in OS X El Capitan

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Disk Utility could always copy an entire disk and create a clone of the target volume. Disk Utility calls this process a Restore, and while the feature is still present, it too underwent changes in OS X El Capitan.

The remaining sections in this article cover using Disk Utility included with OS X Yosemite (10.10) through OS X Leopard (10.5).

Format Your Hard Drive Using Disk Utility

Formatting a hard drive in Disk Utility

Disk Utility's primary purpose is to erase and format a Mac's hard drives. In this guide, you learn how to erase a disk, how to choose different erase options to meet any security need, how to format a drive, including how to zero out data and test the drive during formatting, and finally, how to format or erase a startup drive.

Partition Your Hard Drive With Disk Utility

Partitioning a disk with Disk Utility

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Disk Utility does more than just format a hard drive. You can also use Disk Utility to partition a drive into multiple volumes. Find out how with this guide. It also covers the difference between hard drives, volumes, and partitions.

Add, Delete, and Resize Existing Volumes

Add, Delete, and Resize Volumes in Disk Utility

The version of Disk Utility bundled with OS X 10.5 has a few notable new features, specifically, the ability to add, delete, and resize hard drive partitions without first erasing the hard drive. If you need a slightly larger partition or you would like to split a partition into multiple partitions, you can do it with Disk Utility, without losing the data that's currently stored on the drive.

Resizing volumes or adding new partitions with Disk Utility is straightforward, but you need to be aware of the limitations of both options.

This guide looks at resizing an existing volume, as well as creating and deleting partitions, in many cases without losing existing data.

Using Disk Utility to Repair Hard Drives and Disk Permissions

Disk Utility to Repair Disk Permissions

Disk Utility can repair many common problems that can cause your drive to perform poorly or exhibit errors. Disk Utility can also repair file and folder permission issues that the system may be experiencing. Repairing permissions is a safe undertaking and is often part of routine maintenance for your Mac.

Back Up Your Startup Disk

Disk Utility to Back Up your Startup disk

You have probably heard the admonition to back up your startup disk before performing any system updates. That's an excellent idea, but you may wonder just how to go about it.

The answer is any way you want, as long as you get it done. This guide shows how to use Disk Utility to perform the backup. Disk Utility has two features that make it a good candidate for backing up a startup disk. First, it can produce a bootable backup, so you can use it as a startup disk in an emergency. Second, it's free. You already have it, because it's included with OS X.

Use Disk Utility to Create a RAID 0 (Striped) Array

Using Disk Utility to Create a RAID 0 array

RAID 0, also known as striped, is one of the many RAID levels supported by OS X and Disk Utility. RAID 0 lets you assign two or more disks as a striped set. Once you create the striped set, your Mac sees it as a single disk drive. However, when your Mac writes data to the RAID 0 striped set, the data is distributed across all the drives that make up a set. Because each disk has less to do, it takes less time to write the data. The same is true when reading data. Instead of a single disk having to seek out and then send a large block of data, multiple disks each stream their part of the data stream. As a result, RAID 0 striped sets can provide a dynamic increase in disk performance, resulting in faster ​OS X performance on your Mac.

Use Disk Utility to Create a RAID 1 (Mirror) Array

Disk Utility and RAID 1 (Mirror) Array

RAID 1, also known as a mirror, is one of the many RAID levels supported by OS X and Disk Utility. RAID 1 lets you assign two or more disks as a mirrored set. When you create a mirrored set, your Mac sees it as a single disk drive. When your Mac writes data to the mirrored set, it duplicates the data across all members of the set. This ensures that your data is protected against loss if any hard drive in the RAID 1 set fails. As long as any single member of the set remains functional, your Mac continues to operate normally​ and provides complete access to your data.

Use Disk Utility to Create a JBOD RAID Array

Disk Utility and JBOD RAID array

A JBOD RAID set or array, also known as a concatenated or spanning RAID, is one of the many RAID levels supported by OS X and Disk Utility.

JBOD allows you to create a large virtual disk drive by concatenating two or more smaller drives together. The individual hard drives that make up a JBOD RAID can be of different sizes and manufacturers. The total size of the JBOD RAID is the combined total of all the individual drives in the set.