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Apple Mac Fusion

Fusion Drive, a storage option on some iMac and Mac mini computers, combines a hard drive and flash storage in a single volume for improved performance and storage capacity. If your Fusion Drive is causing slowness/crashing issues or appears as two drives instead of one in the Finder, it's no longer working as a Fusion Drive. This can happen after replacing either drive of your Fusion Drive, or using software to intentionally split them into separate volumes. 

You can continue using the two drives independently, or follow these steps to regain the benefits of having the single logical volume of a Fusion Drive.

1. Turn on your Mac and immediately hold down Command-R or Option-Command-R to start up from macOS Recovery. Release when you see the Apple logo or a spinning globe.

2. When you see the macOS Utilities window, choose Utilities > Terminal from the menu bar.

3. Type this command in the Terminal window, then press Return:
diskutil cs list

Terminal displays additional data about your drives (volumes). Find the string of numbers that appears after ”Logical Volume Group” for the volume named Macintosh HD. It's a number like 8354AFC3-BF97-4589-A407-25453FD2815A.

Example:
+-- Logical Volume Group 8354AFC3-BF97-4589-A407-25453FD2815A
|   =========================================================
|   Name:         Macintosh HD


4. Now simply execute this one command from Terminal:

diskutil coreStorage delete lvgUUID

As listed above, the "lvgUUID" is the unique identifier assigned to the volume. This was shown from the previous step. Once the lvgUUID for the Fusion Drive is located, execute the command, and the fuse will be broken.

Remember that prior to working on any storage related task, it's extremely importance to backup you data from the drive(s) you'll be working on. The process to both create or break a Fusion Drive is destructive, so any/all data contained in those drives will surely be lost.

Type this command in the Terminal window, then press Return:

diskutil list

5. Terminal displays a table of data about your drives. In the IDENTIFIER column, find the identifier for each of the two internal, physical drives that make up your Fusion Drive. Usually the identifiers are disk0 and disk1. One of them should be 128GB or less in size. The other at least 1TB in size.

6. Type the following command, replacing identifier1 and identifier2 with the identifiers you found in the previous step. Then press Return.

diskutil cs create Macintosh\ HD identifier1 identifier2

Example:
diskutil cs create Macintosh\ HD disk0 disk1

If you get a disk unmounting error, enter diskutil unmountDisk identifier, using the first identifier you gathered previously. Then enter same command again using the second identifer.

7. Type this command, then press Return:

diskutil cs list

8. Terminal displays additional data about your drives (volumes). Find the string of numbers that appears after ”Logical Volume Group” for the volume named Macintosh HD. It's a number like 8354AFC3-BF97-4589-A407-25453FD2815A.

Example:
+-- Logical Volume Group 8354AFC3-BF97-4589-A407-25453FD2815A
|   =========================================================
|   Name:         Macintosh HD

9. Type the following command, replacing logicalvolumegroup with the number you found in the previous step. Then press Return.

diskutil cs createVolume logicalvolumegroup jhfs+ Macintosh\ HD 100%

Example:
diskutil cs createVolume 8354AFC3-BF97-4589-A407-25453FD2815A jhfs+ Macintosh\ HD 100%

10. Quit Terminal to return to the macOS Utilities window.

11. Choose Reinstall macOS, then click Continue to begin reinstalling the Mac operating system. Your Mac automatically restarts from your Fusion Drive when done.


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  1. Scott harrington

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