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I wanted to erase the 3 TB Fusion HD on my iMac in order to install a clean system and start from scratch. The erase went fine except right at the end when it said something about core storage... (which I failed to capture, sorry)... and now the machine behaves as though the drive only sort of half exists.

  • There is no 'sub-disk' when I look with Disk Utility - i.e., there is no indented drive listed below "Macintosh HD"
  • The "Erase" tab is absent in Disk Utility
  • All partition options are greyed out in Disk Utility
  • I can boot in Recovery Mode, but I can't reinstall OS X because there is no drive available - it asks me to select a disk, but no disks are listed
  • diskutil sees the drive fine (screenshots below)

In case it's not clear from the images, distil cs list shows:

Logical Volume Group C970ADA-0D05-42AA-9E9C-403ED0E5335
Name: Macintosh HD
Status: Online
(3.1Tb)

    Physical Volume 7DAE3935-D0AD-42AE-AE2A-F6001F09187
    Index: 0
    Disk: disk0s2
    (120Gb)

    Physical Volume BA37C009-F93C-4EAF-9EF3-9C19772BD91C
    Index: 1
    Disk: disk1s2
    (3Tb)

diskutil cs list screenshot

diskutil list shows:

diskutil list screenshot

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1 Answer 1

Reset to default
2

You probably deleted your Logical Volume and the superior Logical Volume Family.

To create a new one boot to Recovery Mode, open Terminal and simply enter:

diskutil cs list #to get the lvgUUID (UUID of the Logical Volume Group)
diskutil cs createVolume lvgUUID type name size

or in your case:

diskutil cs createVolume C970ADA-0D05-42AA-9E9C-403ED0E5335 jhfs+ "Macintosh HD" 100%
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  • Hi There. Massively appreciate the advice.
    – Richard Burke-Ward
    Oct 31, 2015 at 15:00
  • Will let you know if it works.
    – Richard Burke-Ward
    Oct 31, 2015 at 15:01
  • I get an answer saying "the ice (100) must be followed by a letter suffix"... Maybe there was one but it got cut off? I can only see half of that last zero in your post...
    – Richard Burke-Ward
    Oct 31, 2015 at 15:03
  • Just found the percent sign on the end! Let's see if it works now...
    – Richard Burke-Ward
    Oct 31, 2015 at 15:06
  • SUCCESS! You are completely awesome. Many, many thanks. All the best,
    – Richard Burke-Ward
    Oct 31, 2015 at 15:07

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