Add a second external thunderbolt drive

Discussion in 'iMac' started by knight93, Dec 5, 2016.

  1. knight93 macrumors newbie

    Jun 12, 2012
    would it be possible/beneficial for me to add a thunderbolt 500 GB ssd to my 2TB fusion drive in my iMac to make a 2.5TB fusion drive with two forms of flash storage. I've noticed a few things I use frequently have been relegated to HDD storage and it's making things slow like switching accounts or opening iMovie instead of Final Cut Pro

  2. JustMartin macrumors 6502a

    Feb 28, 2012
    It's not recommended (not even sure if it's possible) to make a fusion drive from a combination of internal and external drives. Given how closely they are linked in this configuration, a pulled power or thunderbolt cord could result in you testing how well your backup strategy works. Probably better to make the external drive your primary boot drive and put your applications on that.
  3. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    No it is not possible. You cannot add a third physical drive to the virtual Fusion setup.
  4. Fishrrman macrumors G5


    Feb 20, 2009
    If you have a 2tb fusion drive iMac, the internal flash/SSD is far faster than anything you can plug in "from the outside" (thunderbolt or USB).

    If you want the FASTEST possible performance from the iMac, you need to "de-fuse" the fusion drive, splitting it into a standalone 128gb SSD and a 2tb HDD.

    Put your OS, apps, and basic accounts on the SSD.
    Put everything else (including large libraries of pics, music and movies) on the HDD.

    Keep the SSD "lean and clean", and it will run at peak performance for its entire life.

    You WILL have to learn to manage more than one drive icon on the desktop.
    That's trivial.
    I keep no less than 7 drive icons mounted at all times. I still remember where things go...
  5. johnnyturbouk macrumors 68000


    Feb 9, 2011
    on the yellow [oled] brick road to tech nirvana.
    I did this with my first experiment with fusion, defuse the drive.
    I have now been flash exclusive for some time and could not even fathom going back to spinning disks. On the latest ssds on the imacs late 2015 are phenomenal, I have the 500gb ssd, get 1600mb/s read/write, peaking up to 1950mb/s * read. I began to use an external thunderbolt for everything else.

    I updated my thunderbolt hdd with a 500gb external sandisk ssd, and was given an external usb 3 enclosure with UASP, and tbh, in real world performance and benchmarks, there was little if any tangible difference: I was consistently getting 500/450mbs read/write.


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