External HDD, Internal SSD, Fusion?

Discussion in 'iMac' started by drrich2, Sep 5, 2016.

  1. drrich2 macrumors member

    Jan 11, 2005

    Considering an iMac purchase if new offerings later this year appeal. Would be a 27", hopefully. Not 'handy' and would NOT try to open one & replace an internal HDD.

    If I bought one with a 512 gig or 1 tb internal SSD, and hooked up a thunderbolt external 4 tb HD, given that there are methods to combine 2 drives into a fusion drive, would that work?

    Would there be any disadvantage to this?


  2. maflynn Moderator


    Staff Member

    May 3, 2009
    Yes, I believe it will work.

    Personally, I'd not combine a huge SSD with a external hard drive.

    Don't forget to include a backup strategy.
  3. roadkill401 macrumors 6502


    Jan 11, 2015
    Theoretically, it could be done, but as mayflynn has said, WHY?

    The even bigger problem is that if the Thunderbolt is disconnected, you lose the whole drive. If you were using the only internal SSD, then that is your whole iMac down.

    They do make multibay thunderbolt cases that you can put your own SSD and spinner hard drive into. What I question often is the reality of how fast do you need for certain data. I have about 1.5tb of music files that are sitting on what some will refer to as a brutally slow NAS drive. So yes it takes a whole 300 milliseconds more when I start playing music, but that is only on the first song played and WHO CARES?

    I have all the family photos also sitting on the NAS. they are accessible from all the computers in the house, be it mac or windows, or iPhone or Android. Again, the amount of time to view a photograph doesn't make or break my enjoyment.

    I have a 512gb SSD in my iMac and have all my important documents located on it that are needed for fast speed. I was doing some work for my business and so I moved all the files working on to a folder on my desktop and it was blazing fast. When the work was done, back they went onto the NAS that has full fault tolerance on the drives and gets backed up to a mirror site on a daily basis.

    Sure it is nice to have everything sitting local, but why do I need that and what am I giving up in the process
  4. drrich2 thread starter macrumors member

    Jan 11, 2005
    Thanks. The desire was the simplicity of 'one' volume with everything (including a large Photos library; my stuff won't fit on 1 TB), no hassles with installing things different places & figuring out how to have, say, the library for an ap. on a different drive than the ap. itself (e.g.: iMovie), etc...

  5. Flynnstone macrumors 65816


    Feb 25, 2003
    Cold beer land
    I was in the same boat. All of my data would just fit in a 3T fusion drive. Not big enough for me. I would have preferred a Fusion drive, but ...
    So I bought a 512G SSD version and a 4T external for a start. All video & music & ... (big stuff) goes on the external.
  6. rbart macrumors regular


    Nov 3, 2013
    It will work, but it's not a recommended setup.
    If you want to build a Fusion drive, you don't need so much SSD portion.
    256Gb is enough.
    With so much SSD (512/1Tb), you don't need a FD. You ca put big amount of data (movies, music) on external drive.
    Your data doesn't fit in the 3Tb FD ?
  7. Fishrrman macrumors Pentium


    Feb 20, 2009
    My opinions generally "go against the grain" of others in the forum.
    But I've been running this way for years without problems.

    If you want to get a 512gb SSD (and can afford it), do so.
    Then, consider buying a high-capacity EXTERNAL hard drive to connect via USB.

    BUT -- DON'T try to create a fusion drive between the two.
    Instead, just live with the two separate drive icons.

    There's really nothing to running things this way.
    It does require some forethought on how you want to handle your external storage.

    I have no less than SEVEN drive icons on my desktop at all times, and I seldom have problems remembering "where stuff is".

    If I was buying a new iMac, I'd go for either the 2tb or 3tb "fusion" models, and then "de-fuse" the fusion drive. This would result in a 128gb "standalone" SSD + either a 2tb or 3tb 7200 internal HDD.
    Again, by de-fusing the internal drives, I become the one who controls "where stuff goes", not the OS.
    I'll keep the SSD portion "lean and clean", leaving the HDD portion to store the less-frequently-accessed stuff.
    If you do it this way, the SSD will always run at the highest speeds of which it is capable.

    Then I'd get a 4tb external, partition it, and use it to back up BOTH the internal SSD and the internal HDD.
    I'd use CarbonCopyCloner to create a bootable backup of the SSD, recovery partition and all.

Share This Page