Disk Utility (Yosemite): Create a RAID set

Create a RAID set
Create a RAID set using Disk Utility

Create a Redundant Array of Independent Disks (RAID) set to optimize storage performance and increase reliability in case of a disk failure. You can also create a RAID set that concatenates smaller disks to create one larger disk.

RAID disk sets and concatenated disk sets cannot use some disk management features, such as FileVault disk encryption.

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Create a mirrored RAID set

Protect your data against hardware failure with a mirrored RAID set (also called “RAID 1”). When you create a mirrored RAID set, your data is written to multiple disks so the information is stored redundantly.

You can’t create a RAID set on your startup disk; you must first start up your computer from another disk.

  1. Select one of the disks that you want in the set, then click RAID.

  2. Click Add , then enter a name for the RAID set.

  3. Click the Format pop-up menu, then choose a format.

  4. Click the RAID Type pop-up menu, then choose Mirrored RAID Set.

  5. Drag the disks you want to add to the set to the list on the right.

  6. For each disk, select it, then choose its type from the RAID Type pop-up menu.

    • To use the disk as a mirror at all times, choose RAID Slice.

    • To use the disk as a mirror only when another disk fails, choose Spare. A disk can be a spare in only one RAID set.

      If a disk in the set fails and you have no spares, you must add a new disk to the RAID set in Disk Utility to return to the original number of disks.

  7. To rebuild disks automatically when they’re disconnected and then reconnected, click the Options button, select RAID Mirror AutoRebuild, then click OK.

  8. Click Create.

Create a striped RAID set

A striped RAID set can speed up access to your data.

You can’t create a RAID set on your startup disk, you must first start your computer from another disk.

  1. Select one of the disks that you want in the set, then click RAID.

  2. Click Add , then enter a name for the RAID set.

  3. Click the Format pop-up menu, then choose a format.

  4. Click the RAID Type pop-up menu, then choose Striped RAID Set.

  5. Drag the disks you want to add to the set to the list on the right.

  6. Click the Options button to specify an optimal storage block size for the data stored on the set.

    Set the block size to match the size of data stored on the set.

  7. Click Create.

Create a concatenated disk set

Increase storage space with a concatenated disk set. If you need one large disk, but you have only several smaller disks, you can create a concatenated disk set to use several small disks as one large disk.

  1. Select one of the disks that you want in the set, then click RAID.

  2. Click Add , then enter a name for the RAID set.

  3. Click the Format pop-up menu, then choose a format.

    Usually choose the Mac OS Extended (Journaled) format.

  4. Click Type pop-up menu, then choose Concatenated Disk Set.

  5. Drag the disks you want to add to the set to the list on the right.

  6. Click Create.

If you have a Mac Pro with a Mac Pro RAID card, use RAID Utility. It uses the RAID card for better performance and to create more types of RAID sets.

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Last Modified: Feb 20, 2015
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