What to do with the Fusion Drive after SSD install?

Discussion in 'iMac' started by Yeroon, Oct 11, 2014.

  1. Yeroon macrumors member


    Jun 12, 2012
    Hi all! I just successfully installed an SSD into my late 2012/early 2013 27" iMac. Everything works flawlessly, as I had made a copy of the Macintosh HD via SuperDuper.

    Originally I had a 1 TB HDD with a Fusion Drive (128 GB SSD from Apple). I'm wondering what to do with this original SSD now. I wanted to use it for specific tasks, such as a scratch disk or maybe use it for Bootcamp with Windows 7. 128 GB should be enough (I also have a 3 TB Thunderbolt HDD in RAID1).

    When I open Disk tools (don't know the exact English word, as I use a Dutch OS X version) it says that the Fusion Drive is missing a disk. That's correct, as the 1,1 TB HDD is gone now and the 1 TB SSD is another volume (with a copy of the original disk).

    It's asking if I want to 'rebuild' the Fusion Drive. It's kind of vague what that means. I dont want to rebuild the Fusion Drive itself, I just want to use the 128 GB Apple SSD for other purposes.

    When I click 'Restore' (in Dutch 'Herstel') I get the following question:
    Are you sure you want to fix your system?
    Your damaged internal disks will be erased

    This sounds scary, as if my whole system will be erased. It says DISKS, so that could mean both the 128 GB Apple SSD and my 1 TB SSD replacement. Obviously I don't want to erase my 1 TB SSD - that's the OS X which I'm using now.

    Does anyone know what will exactly happen when you click 'Fix'?

    As mentioned, I want to format the 128 GB Apple SSD only, but this seems the only way to do it. There are probably more people here who replaced their HDD with a SSD while also having a Fusion Drive?

    Attached Files:

  2. thedeske, Oct 11, 2014
    Last edited: Oct 11, 2014

    thedeske macrumors 6502a

    Feb 17, 2013
    Ignore the warning and it should not appear again the next time you launch disk utility. If you let it rebuild, it will erase everything. Apple added this check to the app after they introduced Fusion. The warning looks like a requirement, but it is NOT. You don't require fusion.
    Check the start up disk panel and choose your new SSD.

    Had the same warning when I added an SSD to a late 2012 Mini.
  3. DeltaMac macrumors G3


    Jul 30, 2003
    The reason that you see that message is that you removed part of the fusion drive. The fusion drive is a combined volume that used both the SSD and the HDD. When you upgraded the SSD, the HDD part of the fusion drive is still in place. The Disk Utility wants to "fix" that by repairing the volume. The process WILL remove all data from both the SSD and the HDD.
    I think there's a terminal command that you can use to remove that phantom volume - someone else may know what that is.
  4. thedeske macrumors 6502a

    Feb 17, 2013
    Rename it something other then Macintosh HD & Erase it
  5. Yeroon thread starter macrumors member


    Jun 12, 2012
    Renaming it, in the Finder or Disk Utilities, isn't possible. I can't access it.

    However, based on the other replies I found the command to disable the Fusion Drive via Terminal. But this is based on an active Fusion Drive. http://macs.about.com/od/diyguidesprojects/ss/Split-Your-Fusion-Drive-Apart_3.htm#step-heading

    The article mentions a Logical Volume Group and a Logical Volume. I have a Logical Volume Group and a Physical Volume. (see screenshot)

    Would it be safe to delete the Logical Volume Group?
    That would be: diskutil cs deleteVolume C9DFDA69-C057-4A66-B820-A2CE62AFE874 ?

    Attached Files:

  6. thedeske macrumors 6502a

    Feb 17, 2013
    First, make a fresh backup of the new drive, then you can play.
    I would try to simply "Get Info" on the 120 in the finder and rename it there. Select everything on the drive/trash/delete. At that point open disk utility, select and format the drive - basic Mac OS Extended

    The terminal steps are looking for the fusion/core volume drives, so you can try that if needed. Your new drive is not part of that volume. It should be OK if you run the terminal commands, but a fresh backup/clone of the new system drive will keep you safe in the process. You can always boot the external fresh clone and wipe everything out/ reclone.

    Good Luck
  7. finepiks macrumors member

    Dec 5, 2012
    Just reviving an old thread to add that I did use the "Fix" option and it only sorted the on board SSD without any issues at all. I was then able to reformat and rename it from within Disk Utility. It now shows as an additional drive in Finder.

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