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I created a fusion drive on my MacBook Pro running Mountain Lion and it worked like a charm for a while, but it somehow got corrupted.

Now I am unable to reformat or repartition the whole thing.

> diskutil cs list

CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 40B334F6-6988-4727-9A2B-48E7999F4047
    =========================================================
    Name:         MacintoshHD
    Size:         558926610432 B (558.9 GB)
    Free Space:   135995392 B (136.0 MB)
    |
    +-< Physical Volume AC91E9F8-CAAA-48B9-A000-93E559F5D2DD
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk0s2
    |   Status:   Online
    |   Size:     59162722304 B (59.2 GB)
    |
    +-< Physical Volume 1319D374-879E-418F-88EF-5AA163B4105C
    |   ----------------------------------------------------
    |   Index:    1
    |   Disk:     disk1s2
    |   Status:   Online
    |   Size:     499763888128 B (499.8 GB)
    |
    +-> Logical Volume Family 3E85E6B1-4E99-4CBD-A34E-E720A090F373
        ----------------------------------------------------------
        Encryption Status:       Unlocked
        Encryption Type:         None
        Conversion Status:       NoConversion
        Conversion Direction:    -none-
        Has Encrypted Extents:   No
        Fully Secure:            No
        Passphrase Required:     No
        |
        +-> Logical Volume 76A3020B-B3C2-4905-9E09-2EBB5470261C
            ---------------------------------------------------
            Disk:               disk2
            Status:             Online
            Size (Total):       556000083968 B (556.0 GB)
            Size (Converted):   -none-
            Revertible:         No
            LV Name:            HD
            Volume Name:        HD
            Content Hint:       Apple_HFS

> diskutil cs delete 40B334F6-6988-4727-9A2B-48E7999F4047

Started CoreStorage operation
Ejecting Logical Volumes
[ \   \   \   \   \   \   \   \   \   \   \   \   \   \   ]

I remain stuck there and cannot delete the Logical Volume Group, or do anything at all on it's components.

By now I would be satisfied if I could just wipe /dev/disk0 and /dev/disk1 completely and start over, but unfortunately this does not work either :

> diskutil zeroDisk /dev/disk0

Started erase on disk0
Error: -69879: Couldn't open disk
Underlying error: 16: POSIX reports: Resource busy

I hope someone will be able to help me, I have absolutely no idea how to recover this computer!

I also posted this question on Apple's forums, but I expect a better answer answer and more importantly a longer shelf life!

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2 Answers 2

I was able to delete a mess I made trying to delete my Raid 10 in diskutil (which ended up looking similar to above) using the commands below in Terminal.app. May or may not work with fusion but it's easier than booting up again.

Get rid of the volume - copy paste the logical volume name where it says "Logical Volume Name", without the quotes:

diskutil cs deleteVolume "*Logical Volume Name*"

Free the disk - copy paste the volume name where it says "Physical Volume Name", without the quotes:

diskutil cs removeDisk "*Physical Volume name*" 

Repeat these steps as needed.

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up vote 0 down vote accepted

While I was unable to "cleanly" solve my problem, I managed to reset everything by booting in single-user mode from an external hard drive (reboot holding ⌘-S) and overwriting the disk directly with

cat /dev/random > /dev/disk0
^C
cat /dev/random > /dev/disk1
^C

Then I rebooted and I could reformat the drives (actually, I created another fusion drive using these directives).

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