Fusion drive questions

Discussion in 'macOS Sierra (10.12)' started by Blueline111, Dec 9, 2018.

  1. Blueline111 macrumors newbie

    Dec 26, 2013
    I created a fusion drive three years ago consisting of an internal 1TB mechanical HD and an internal 250 GB 840 evo SSD in a mid-2011 iMac running Sierra. Total HD space is 1.19 TB with 383 GB of free space remaining. I have purchased a 1 TB 860 evo SSD to replace the mechanical drive.

    If I break the fusion drive and use just the 1 TB SSD for my system the SSD will be nearly full. The 250 GB SSD will just be a separate drive. My other option is to keep the fusion drive using both SSDs.

    I'm not sure which is the best way to go although I'm leaning towards keeping the fusion drive. I appreciate your input as to which way to go. What are the pros and cons?
  2. Wando64 macrumors 6502a


    Jul 11, 2013
    As they are both SSDs, the suggestion of jbarley seems a better option than a Fusion drive with would add complication for nothing, quite possibly slowing the performance down for little benefit.

    My inclination though, would be to identify a subset of your data that could logically be separated from the rest and fit it onto the smaller disk. Not a perfect solution, but neater, in my opinion.

    EDIT: in fact, 250GB would be more than large enough to accommodate your OS and all of your apps. leaving the 1tb disk entirely available for your data.
  3. FlorisVN macrumors 6502


    Nov 8, 2013
    I would setup a RAID0 or RAID1 with 2 ssd's in a iMac 2011.
    when using RAID0 make sure you have good backups !
  4. Blueline111 thread starter macrumors newbie

    Dec 26, 2013
    Thanks to all who responded with suggestions. Another option occurred to me today. What if I replace the 250 GB SSD with the 1TB SSD and kept the fusion drive with the mechanical HD? It sounds less complicated than having a concatenated disk set. Would I take much of a performance hit?
  5. Wando64, Dec 11, 2018
    Last edited: Dec 11, 2018

    Wando64 macrumors 6502a


    Jul 11, 2013
    I also have a a 1TB SSD and a 1TB HDD on my Mini, and I have debated as to whether it would be worthwhile joining them as a Fusion drive.
    In theory you should see almost no performance hit, as pretty much all of the data you use regularly will permanently reside on the SSD, whereas only stuff you never use will be relegated to the HDD.
    But then, why not keeping two separate drives and put the stuff you rarely use onto the HDD?
    That is what I have decided to do in the end, however I would be interested in hearing the experience of someone going the other way with a 50/50 2TB Fusion drive.

    EDIT: I should add that one of the reasons for my decision to keep them separate is that I intend to upgrade to Mojave in the near future and I understand that APFS doesn’t much like homemade Fusion drives. I’d be happy if anybody could confirm otherwise.

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5 December 9, 2018