Disk Utility Partitions Wrong Part of Fusion Drive

bootcampdisk-utilityfusion-drivepartition

I have a question about my iMac 2015 Fusion Drive. I replaced my spindle with a SATA SSD 512gb drive. Here are the commands I used from an online instruction set to remake the Fusion Drive:

diskutil list

And saw that PCIE SSD was disk1, SATA SSD was disk0 so I ran:

diskutil coreStorage create Fusion /dev/disk1 /dev/disk0
diskutil coreStorage createVolume [lvgUUID] jhfs+ "Macintosh HD" 100%

Where [lvgUUID] was the unique Core Storage ID string

This worked great, I installed macOS and everything was grand except when I went into Disk Utility, I tried to make a partition, I am limited to making one the size of my tiny 24GB SSD and when I do make one under that size it uses the PCIE for the partition instead of the larger SATA drive. This is making it impossible to get Bootcamp up and running, since the Bootcamp Setup Assistant will not let me make a partition claiming I don't have enough free space.

Will it work to just switch the order of disk0 and disk1? Any thoughts greatly appreciated!

diskUtil cs list output:

CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 7D87AFDD-C64A-4AC2-B8E4-6C098F67A384
    =========================================================
    Name:         FUSE
    Status:       Online
    Size:         534804156416 B (534.8 GB)
    Free Space:   176128 B (176.1 KB)
    |
    +-< Physical Volume 9A2B9DD4-3C79-46C2-BB4F-886B5A6B9C73
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk1s2
    |   Status:   Online
    |   Size:     23037939712 B (23.0 GB)
    |
    +-< Physical Volume 3BE6757D-AE99-4C70-A0B3-CC16725BA627
    |   ----------------------------------------------------
    |   Index:    1
    |   Disk:     disk0s2
    |   Status:   Online
    |   Size:     511766216704 B (511.8 GB)
    |
    +-> Logical Volume Family 8AB4FCEE-8DDF-487E-A9B9-F351BE591D2E
        ----------------------------------------------------------
        Encryption Type:         None
        |
        +-> Logical Volume 45E7132B-2676-450E-85D6-636EA3DFDC4F
            ---------------------------------------------------
            Disk:                  disk2
            Status:                Online
            Size (Total):          526809563136 B (526.8 GB)
            Revertible:            No
            LV Name:               Macintosh HD
            Volume Name:           Macintosh HD
            Content Hint:          Apple_HFS
            LVG Type:              Fusion, Sparse

diskUtil list output:

Charles-iMac:~ tinyhouse$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *512.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage FUSE                    511.8 GB   disk0s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3

/dev/disk1 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         24.0 GB    disk1
   1:                        EFI EFI                     314.6 MB   disk1s1
   2:          Apple_CoreStorage FUSE                    23.0 GB    disk1s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3

/dev/disk2 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                            Macintosh HD           +526.8 GB   disk2
                                 Logical Volume on disk1s2, disk0s2
                                 45E7132B-2676-450E-85D6-636EA3DFDC4F
                                 Unencrypted Fusion Drive

Best Answer

To create a proper "Fusion Drive" in your case, you first have to create a normal CoreStorage Logical Volume Group with one physical volume and one logical volume. Then you have to install macOS. In a last step you have to add the second physical volume to the CoreStorage Logical Volume Group and expand the existing logical volume.

  • backup your main volume
  • boot to Internet Recovery Mode (or a macOS installer thumb drive)

  • get all necessary listings:

    diskutil list
diskutil cs list

  • destroy the LVG:

    diskutil cs delete lvgUUID #lvgUUID: UUID of the Logical Volume Group
  • completely erase both disks (each to one volume with the names e.g. "data1" and "data2" but not "Macintosh HD")
  • get the device identifiers again: diskutil list

  • create a new LVG and LV on the larger disk (here I assume the 500 GB SSD has the disk identifier disk0):

    diskutil cs create Fusion disk0
diskutil cs list
diskutil cs createVolume lvgUUID jhfs+ "Macintosh HD" 100%
  • Install macOS to "Macintosh HD"

  • After configuring macOS open Terminal and enter

    diskutil list
diskutil cs list

  • add the 24 GB disk (here I assume the disk identifier is disk1) to the LVG:

    diskutil cs addDisk lvgUUID disk1

  • Expand the main system volume:

    diskutil cs resizeVolume lvUUID size #with size e.g. 526800m

    If you get an error "Error: -69720: There is not enough free space in the Core Storage Logical Volume Group for this operation" choose a slightly smaller size like 526400m or 526000m

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