Questions on replacing "fusion drive"

Discussion in 'iMac' started by tominco, Dec 9, 2018.

  1. tominco macrumors member

    Joined:
    Mar 14, 2008
    #1
    I have a 27" late 2013 iMac with an apparently failing fusion drive. I understand that the drive is a 1TB SATA HDD and a 128GB PCIe SSD "blade." I have no idea which portion is failing, but disk performance is down the toilet, and at one point the Mac was reporting the drives were split. Oddly, they are back together now. Anyway, I want to replace the HDD with OWC's 2TB SSD kit.

    My question is what about the blade? Do I have to remove it? Can I remove it and not replace it? If I don't remove it, can I just ignore it?

    Obviously, leaving it and ignoring it is the easiest, and I'd prefer not to spend money to replace it, as I doubt it will help much with an SSD as primary drive even though the PCIE blade is faster than a SATA drive, plus I don't trust it anymore.

    thanks!
     
  2. chscag macrumors 68040

    chscag

    Joined:
    Feb 17, 2008
    Location:
    Fort Worth, Texas
    #2
    If you find the 128GB PCIe blade SSD is okay, you can always place it in an external enclosure and use it for storage after removing it from your iMac. I'm not sure if OWC sells an enclosure or adapter for that particular Apple blade SSD, but you can check with them when you purchase the 2TB SSD kit from them.
     
  3. Fishrrman macrumors P6

    Fishrrman

    Joined:
    Feb 20, 2009
    #3
    OP --

    Does the iMac happen to be a 3tb fusion drive model, by any chance?
    Seems to me that the 2013 iMacs had a run of bad 3tb HDDs in these, and that Apple (at least for a while) had a free replacement program for them.

    This replacement program may no longer be in effect.

    In any case, if you suspect the HDD portion has failed, but the SSD portion remains ok, it's possible to "separate" the fusion drive into "standalone" SSD and HDD.

    You could then set the SSD to be the boot drive.
    Of course, with only 128gb available, you'd have to be careful about what you kept on it.
    I would suggest the OS, apps, and "stripped down" user folders.
    Keep large libraries on an EXTERNAL USB3 hard drive (could be either an HDD or an SSD).
    If the internal HDD has failed, you could just "leave it in place, empty and unused".

    Only a few minutes ago I was browsing old files on my Mac, and came across this URL:
    http://arstechnica.com/apple/2012/11...-fusion-drive/

    It contains instructions on how to "UN-fuse" the fusion drive, using the terminal.
    Perhaps it may be of some use to you.

    From my archives, here are the commands I think you'll need:
    ==========================
    Boot in recovery mode, then open terminal, and type these commands:

    diskutil cs list

    This command will show you the IDs you need to delete fusion drive.

    diskutil cs deleteVolume < insert fusion logical volume ID here >
    diskutil cs delete < insert coreStorage logical volume group ID here >

    These commands will split the drives apart. Once the drives are separated, you can rename those drives in Terminal, because you can't use Disk Utility: it will try to fix the Fusion Drive for you.

    diskutil list

    This command will show you the identifier for the two drives, that you'll use this way:

    diskutil rename disk0s2 Macintosh HD
    diskutil rename disk1s2 Data HD

    Exit terminal, click on "Install OS X" and select the SSD, and you're good to go. Once in disk utility in OSX, the drives will be listed normally.
     
  4. nambuccaheadsau macrumors 68000

    nambuccaheadsau

    Joined:
    Oct 19, 2007
    Location:
    Nambucca Heads Australia
    #4
    The normal 2/3TB drive was a 7200rpm Seagate drive and Apple did a recall on these in the early days of the late 2013 27" iMac. If the drive is in fact a 1TB SSD do as the fiisho suggests above by 'defusing' the PCII-e blade drive and using the SSD as the boot drive. He may tell stories about his fish but never about Macs.
     

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3 December 9, 2018