How to erase and create a Fusion Drive

You are doing this at your own risk! Make backups! Think twice!

The Problem

Maybe you destroyed the partition map, the partitions won't resize or the Mac OS X Installer just refuses to install on the Fusion Drive.

The Solutions

Solution 1 (better)

• Boot in Recovery Mode (⌘-R) or NetBoot
• Open Terminal
• Erase Fusion Drive

-bash-3.2# diskutil coreStorage list
CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 529DC00D-FA54-49AD-B7F7-F98E33EBFCE8
   =========================================================
   Name:         Macintosh HD
   Status:       Online
   Size:         1120333979648 B (1.1 TB)
   Free Space:   114688 B (114.7 KB)
   |
   +-< Physical Volume 0CDB5E98-69B0-4BC1-A20F-0B9B5BC20CC7
   |   ----------------------------------------------------
   |   Index:    0
   |   Disk:     disk0s2
   |   Status:   Online
   |   Size:     120988852224 B (121.0 GB)
   |
   +-< Physical Volume B3B961EC-058C-48E4-A7D2-828829900694
   |   ----------------------------------------------------
   |   Index:    1
   |   Disk:     disk1s2
   |   Status:   Online
   |   Size:     999345127424 B (999.3 GB)
   |
   +-> Logical Volume Family C137DC69-C3DC-42D6-9896-AA2F26824C0F
       ----------------------------------------------------------
       Encryption Status:       Unlocked
       Encryption Type:         None
       Conversion Status:       NoConversion
       Conversion Direction:    -none-
       Has Encrypted Extents:   No
       Fully Secure:            No
       Passphrase Required:     No
       |
       +-> Logical Volume 1D714029-D6B4-4FC0-BCCC-666F10FC0ED0
           ---------------------------------------------------
           Disk:               disk3
           Status:             Online
           Size (Total):       1111826497536 B (1.1 TB)
           Size (Converted):   -none-
           Revertible:         No
           LV Name:            Macintosh HD
           Volume Name:        Macintosh HD
           Content Hint:       Apple_HFS
-bash-3.2# diskutil coreStorage delete529DC00D-FA54-49AD-B7F7-F98E33EBFCE8
Started CoreStorage operation
Ejecting Logical Volumes
Destroying Logical Volume Group
Erasing disk0s2
Initialized /dev/rdisk0s2 as a 113 GB HFS Plus volume with a 16384k journal 
Mounting disk
Erasing disk1s2
Initialized /dev/rdisk1s2 as a 931 GB HFS Plus volume with a 81920k journal
Mounting disk
Finished CoreStorage operation
-bash-3.2# diskutil list
/dev/disk0
  #:                       TYPE NAME                    SIZE       IDENTIFIER
  0:      GUID_partition_scheme                        *121.3 GB   disk0
  1:                  Apple_HFS                         209.7 MB   disk0s1
  2:                  Apple_HFS Untitled                121.0 GB   disk0s2
  3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3
/dev/disk1
  #:                       TYPE NAME                    SIZE       IDENTIFIER
  0:      GUID_partition_scheme                        *1.0 TB     disk1
  1:                  Apple_HFS                         209.7 MB   disk1s1
  2:                  Apple_HFS Untitled                999.3 GB   disk1s2
  3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3
/dev/disk2
  #:                       TYPE NAME                    SIZE       IDENTIFIER
  0:     Apple_partition_scheme                        *1.3 GB     disk2
  1:        Apple_partition_map                         30.7 KB    disk2s1
  2:                  Apple_HFS Mac OS X Base System    1.3 GB     disk2s2
/dev/disk4
  #:                       TYPE NAME                    SIZE       IDENTIFIER
  0:                            untitled               *524.3 KB   disk4
[…]
-bash-3.2#

• Fusion Drive Recovery:
  Close Terminal and open Disk Utility, click "Fest" (engl. "Fix"):
  
• Done!

Solution 2 (worse)

This solution permanently erases the Recovery Partition - that's why it's worse. But it might work better in some cases (or if you want to set up a Fusion Drive from non-Apple-components.

• Erase Fusion Drive
  • diskutil coreStorage list
    (to get Logical Volume Group UUID)
  • diskutil coreStorage delete <Logical Volume Group UUID>
    (Erasing the Fusion Drive)
• Fusion Drive creation
  • diskutil list
    (find disk devices)
  • diskutil coreStorage create myLogicalVolGroup /dev/disk1 /dev/disk2
    (Logical Volume Group creation, note the new Logical Volume Group UUID)
  • diskutil coreStorage createVolume <Logical Volume Group UUID> <type> <name> <size>, f.e. diskutil coreStorage createVolume 50B457C3-ADC6-4EDC-9ABA-FD8C6EEDE69A jhfs+ "Macintosh HD" 100%
    (Logical Volume creation)

---

• Links
  • http://www.macworld.com/article/2015664/how-to-split-up-a-fusion-drive.html
  • http://www.macworld.com/article/2014011/how-to-make-your-own-fusion-drive.html
• Notes: