Fusion drive split into 3 partitions... How do I format the drive back to 1?

Discussion in 'iMac' started by Zellio, Apr 20, 2014.

  1. Zellio macrumors 65816


    Feb 7, 2012
    Hi, since I now have a dedicated large SSD (Over thunderbolt..) I want to format my 3 tb iMac drive and use it all as a windows partition. However, the drive is in 3 partitions and won't let me reformat it back to 1!
  2. omvs macrumors 6502

    May 15, 2011
    I think you have to do it via Terminal & the diskutil command. If you're comfortable with command line operations (or have a friend who is), what you basically want to do is:

    Boot up in recovery mode (Command-R I think when powering on)
    Open up the terminal application

    diskutil cs list
    (this will show you the core storage partitions - find the one that matches your fusion setup - you need its Logical Volume Group ID for the next step)
    diskutil cs delete (volumeid)

    At that point, you should be able to use the GUI disk util to set things up however you want. Or you can just set it all up using the command line diskutil options. You'll basically want to do "diskutil list" to find your 3TB drive, then "diskutil partitionDisk disk# GPT JHFS+ MacintoshHD 100%" and that will rewrite the disk as one big partition, non-fusion.

    NOTE: If you ever want to recreate the fusion, I think you have to use the terminal to do it. Its a bit more involved (instructions can be found on web), so I would be caution against any of this if you're not prepared to spend a lot of time or not very computer literate.
  3. Zellio thread starter macrumors 65816


    Feb 7, 2012
    Yup, I got it, the damn thing had two logical volumes (I don't know why) And I hate to delete one and then check the diskutil cs list again as the second one seemed to change it's logical volume :rolleyes:

    Now It's one 3tb drive again.

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