This article describes how to use disk utility to create a JBOD RAID array on a Mac with macOS Yosemite or earlier. El Capitan and newer versions of macOS removed RAID capability from Disk Utility. Instead, use Terminal or an app such as SoftRAID Lite.

What You Need

The hard drives you use in the JBOD set can be of different sizes and from different manufacturers. If you’re working on a Mac Pro, you can use any available internal drive bays. Otherwise, you’ll need one or more external drive enclosures.

Erase the Drives Using the Zero Out Data Option

First, you’ll erase the hard drives within the JBOD RAID set. To reduce the risk of drive failures in the JBOD array, use one of the Disk Utility security options, Zero Out Data, when each drive erases.

When you zero out data, you force the hard drive to check for bad data blocks during the erasure process and mark any bad blocks as not to be used. This step decreases the likelihood of losing data due to a failing block on the hard drive. It also increases the time it takes to erase the drives from a few minutes to an hour or more per drive.

  • Launch Disk Utility and select one of the hard drives for the JBOD RAID set from the list in the sidebar. Select the drive, not the volume name that appears indented under the drive’s name. Then, click the Erase tab.
  • From the Volume Format drop-down menu, select Mac OS X Extended (Journaled) as the format to use.
  • Enter a name for the volume in the Name field.
  • Select Security Options > Zero Out Data and click OK.
  • Click Erase.
  • Repeat this process for each additional hard drive that will be part of the JBOD RAID set. Give each hard drive a unique name.

Create the JBOD RAID Set

After the drives are erased, build the concatenated set.

Launch Disk Utility and select one of the hard drives for the JBOD RAID set from the list in the sidebar. Select the drive, not the volume name that appears indented under the drive’s name. Then, click the Erase tab.

From the Volume Format drop-down menu, select Mac OS X Extended (Journaled) as the format to use.

Enter a name for the volume in the Name field.

Select Security Options > Zero Out Data and click OK.

Click Erase.

Repeat this process for each additional hard drive that will be part of the JBOD RAID set. Give each hard drive a unique name.

  • In Disk Utility, select one of the hard drives from the drive/volume list in the left sidebar. Click the RAID tab.
  • Enter a name in the field next to RAID Set Name for the JBOD RAID set that displays.
  • Select Mac OS Extended (Journaled) from the Format drop-down menu.
  • Select Concatenated Disk Set in the RAID Type field.

Add Slices (Hard Drives) to Your JBOD RAID Set

It’s time to add members, or slices, to the set and create the finished RAID volume.

In Disk Utility, select one of the hard drives from the drive/volume list in the left sidebar. Click the RAID tab.

Enter a name in the field next to RAID Set Name for the JBOD RAID set that displays.

Select Mac OS Extended (Journaled) from the Format drop-down menu.

Select Concatenated Disk Set in the RAID Type field.

  • Drag one of the hard drives for the array from the left sidebar of Disk Utility onto the RAID array name you created in the previous step.
  • Drag the remaining hard drives intended for the JBOD RAID set onto the RAID array name. A minimum of two slices, or hard drives, is required for a JBOD RAID. Adding more than two further increases the size of the resulting JBOD RAID.
  • Click Create. A Creating RAID warning sheet drops down, reminding you that all data on the drives that make up the RAID array will be erased.
  • Click Create to continue.

During the creation of the JBOD RAID set, Disk Utility renames the individual volumes that make up the RAID set to “RAID Slice.” It then creates the actual JBOD RAID set and mounts it as a normal hard drive volume on your Mac’s desktop.

Drag one of the hard drives for the array from the left sidebar of Disk Utility onto the RAID array name you created in the previous step.

Drag the remaining hard drives intended for the JBOD RAID set onto the RAID array name. A minimum of two slices, or hard drives, is required for a JBOD RAID. Adding more than two further increases the size of the resulting JBOD RAID.

Click Create. A Creating RAID warning sheet drops down, reminding you that all data on the drives that make up the RAID array will be erased.

Click Create to continue.

The total capacity of the JBOD RAID set you create equals the combined total space of all members of the set, minus some overhead for the RAID boot files and data structure.

You can now close Disk Utility and use your JBOD RAID set as if it were any other disk volume on your Mac.

Extra: Tips for Using Your New JBOD RAID Set

As a concatenated disk set, your JBOD RAID array is not as susceptible to drive failure problems as a RAID 0 array. Nevertheless, you should still have an active backup plan in place if you need to rebuild your JBOD RAID set. Consider the use of backup software that runs on a predetermined schedule.

It is possible to lose one or more disks in a JBOD RAID to hard drive failure and still have access to the remaining data. That’s because data stored on a JBOD RAID set remains physically on individual disks. Files do not span volumes, so data on any remaining drives should be recoverable.

That does not mean that recovering data is as simple as mounting a member of the JBOD RAID set and accessing it with the Mac’s Finder. You might need to repair the drive and use a disk recovery application.

About JBOD RAID Sets

No matter what you call it—JBOD, concatenated, or spanning—this RAID type is about creating larger virtual disks. JBOD—the acronym for Just a Bunch Of Disks—is not a recognized RAID level, but Apple and most other vendors that created RAID-related products included JBOD support with their RAID tools.

Among the many uses for JBOD RAID is expanding the effective size of a hard drive—just the thing if you have a file or folder that’s getting too large for the current drive. You can also use JBOD to combine smaller drives to serve as a slice for a RAID 1 (Mirror) set.

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