Who has split their Fusion drives up?

Discussion in 'iMac' started by maflynn, Jan 17, 2016.


Who has split their Fusion drive

  1. Yes I split it and its great

    5 vote(s)
  2. I split it, but fused it back because I preferred the fusion drive.

    3 vote(s)
  3. No, I'd rather keep it as a Fusion drive.

    6 vote(s)
  4. Maybe, I'm on the fence.

    2 vote(s)
  1. maflynn Moderator


    Staff Member

    May 3, 2009
    I keep kicking this around myself, so I'm curious to see who actually has done it, or decided not to split it up.

    I can see advantages for both options, i.e., letting the system determine what goes in the flash drive, and keeping it logically as a single drive. Conversely having control of what goes where is a nice option as well.
  2. bent christian Suspended

    bent christian

    Nov 5, 2015
    I have been using a Fusion drive for a few months. The system seems to be adjusting better with time. Outside of a few very specific scenerios, I don't see any advantage to splitting up the drives. Splitting the drives up just because is a bad idea. It will lead to slower overall performance for most users. If you don't know why you should, don't.
  3. dimme macrumors 68000

    Feb 14, 2007
    SF, CA
    So far I am happy with the performance of the fusion drive. I have my 2 TB drive well over half full an like the face I do not have to manage what is where. If I was to do anything in the future I would go with a 2 TB SSD in a thunderbolt enclosure, but I do not think they do not exist and the money to purchase such a drive does not exist. But who knows maybe next year. I thought about going with a pure SSD iMac but the cost for 512 SSD was high and a got a post christmas deal on the stock iMac with the fusion so the price difference was great. So i figured if I went with the SSD most of my photoshop files would be on my slower externals.
  4. ApfelKuchen macrumors 68040

    Aug 28, 2012
    Between the coasts
    Why break something that works?

    On the other hand, if you want a tower so you can have multiple internal drives, then this is the only way to get something approximating that configuration from Apple. Break the Fusion, and use the drives however you wish. You believe you can get more efficient and effective use of that SSD, then go for it.

    Cache management is the kind of task a computer excels at. If you trust the OS to manage a cache, any cache (and RAM is a cache), then why distrust this one? The computer manages on-CPU cache, RAM, HDD-based RAM cache, app-specific caches. Streaming media buffering... cache. Can you imagine managing any of those? If I want my data to benefit from SSD, I don't want to have to manually move those files to SSD, then remember to move them back to HDD when I'm done. And I definitely don't want to get into the kind of versioning issues that can arise when the same file resides on two drives.

    I, for one, have never liked multi-drive configurations. RAID does it for well-known reasons. If you need redundancy, there's no other way. But otherwise... I've always hated the, "Which drive is it on?" game. Treating physical drives like physical filing cabinets makes no sense to me. "Accounts Receivable in this cabinet, Accounts Payable in that one." Accounts Receivable cabinet half-empty, Accounts Payable over-stuffed. Forget about it!
  5. maflynn thread starter Moderator


    Staff Member

    May 3, 2009
    I never said it doesn't work, but I've seen people here and elsewhere state that they broke up the fusion drive.

    I can see some arguments for doing this, such as wanting to have a bootcamp partition on the SSD, with Fusion it goes on the slower spinning drive.
  6. garyleecn macrumors 6502a

    Jul 25, 2014
    Yes it is possible
    When (re)installing the system, use the terminal to delete the corestorage (command should be something like diskutil corestorage -list and then diskutil corestorage delete UDID)
    Then you will have two seperate drives.
    One key thing is NOT to go into disk utility to check if it was successful, once you open disk utility, system will automatically create fusion for you.

    Bottom line is, it is possible.
    If you need I can try to find a step by step guide for you
  7. TPadden macrumors 6502a

    Oct 28, 2010
    Broke it, replaced the internal spinner with another SSD and put the Spinner in an external USB. Only use the spinner occasionally.
  8. JustMartin macrumors 6502a

    Feb 28, 2012
    Apart from bootcamp, I think the majority of people who split their Fusion Drives do it because they a) have time to manage storage b) think they can do a better job than the OS. Personally, I don't fall into either camp.
  9. bogg macrumors 6502


    Apr 12, 2005
    C) doesn't trust combined storage with their valuable data (due to insufficient backups probably)
  10. Erdbeertorte, Jan 19, 2016
    Last edited: Jan 19, 2016

    Erdbeertorte Suspended

    May 20, 2015
    I split it because I did not have much data and wanted to use the HDD for Time Machine backups.

    But I returned the iMac and now have one without Fusion Drive.


    That was also a reason.

    Edit 2:

    I even had two partitions on the 2TB HDD. The second one mirrored the SSD, for the case it might fail and I would be able to easily use the iMac without sending it in to Apple.

    Of course I had an external backup disk too.
  11. MadDane macrumors 6502a

    Apr 5, 2015
    I have made my own Fusion Drive approximately three years ago from a 2TB HDD and 128GB SSD (very similar to Apple's current offering). I don't use Boot Camp and I have Time Machine running at all times over Wi-Fi. I think it works pretty well and this way I do not have to worry about where what goes. I can feel the difference between the Fusion Drive and the SSD in my rMBP so I would like to upgrade to a larger SSD and ditch the HDD altogether at some point. But for now the Fusion Drive is working out fine.
  12. Lankyman macrumors 68000

    May 14, 2011
    I have internal multi-drives on my iMac and the system works really really well. I decided what I wanted on my SSD and what to put on the HDD e.g. videos, music, photos etc. I use sym-links to access files on the HDD. This is a very good solution. This multi-drive scenario 'just works'.
  13. Erdbeertorte Suspended

    May 20, 2015
    I often read that. But strangely my Disk Utility did not recognize that it had been a Fusion Drive before. I had to use the Terminal to recreate it again before returning the iMac.

    Maybe it's Skylake or getting El Capitan over Internet Recovery that changed it.
  14. dimme macrumors 68000

    Feb 14, 2007
    SF, CA
    I believe the disk utility in El Captain does not automatically re-create the fusion drive.
  15. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    You need to be in Internet recovery (command-option-r boot) for Disk Util to give you the "Fix" prompt to create the Fusion drive. I don't believe it will do it from regular recovery. The bottom of this support doc. seems to support that.

    To separate you could just go to Internet recovery then enter the line below in Terminal.

    diskutil cs delete "Macintosh HD"
    Then when the Fix prompt comes up when you launch DU, just click ignore and format the two drives normally.

  16. dimme macrumors 68000

    Feb 14, 2007
    SF, CA
    Intersting I had to re-creat mine after a Bootcamp fiasco. I had to do it all in terminal and then just format it in disk utility
  17. garyleecn macrumors 6502a

    Jul 25, 2014
    yes, el capitan does have something to do with it, not skylake though.
    i have both 1gen and 2gen 5k iMac, i tried to wipe the hard drive and reinstall el capitan, both gave me errors when wiping in disk utility. so i have to manually use commands to delete/create fusion myself.

    el capitan does have some change on handling fusion in disk utility, but still, we can separate it.
  18. danielcorrea89 macrumors newbie

    Jul 14, 2019
    I have done it after using Fusion Drive for a year. The performance improvement on the pure SSD is mind-blowing...
    I regret not doing it earlier.

    The only issue is that 120GB is limited and must be used wisely. I can't really use bootcamp in SSD with that little space, but I can have a Windows VM in Parallel which I use to work with development apps. It's all blazing fast.

    Now I use the 2TB HDD occasionally to store some media, and the 120GB SSD to store all apps and my work VM.

    It feels like a new Mac.

    Screen Shot 2019-07-15 at 9.38.27 AM.png

    Re: yes, I did a better job than the OS
  19. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    About to do this on my old late 2013 model my son uses. 3TB HDD haas failed and won'tr repair and seems to slow apps down hreatly.
  20. Fishrrman macrumors P6


    Feb 20, 2009
    nambu wrote:
    "About to do this on my old late 2013 model my son uses. 3TB HDD haas failed and won'tr repair and seems to slow apps down hreatly."

    I believe "splitting the fusion drive" would make good sense in your case.

    Split them apart and you can now try to "localize" the problem.

    If it's on the HDD portion, but the SSD portion seems to be ok, then I would:
    a. Install the OS, apps, and slimmed-down account(s) on the SSD
    b. Erase the HDD (if possible), then just "let it be" -- unused.
    c. Use external USB3 storage (HDD or SSD) for additional storage space.
  21. ApfelKuchen macrumors 68040

    Aug 28, 2012
    Between the coasts
    Here's the thing - if you have a 121 GB SSD in a Fusion drive you have as much Flash storage as many laptop owners live with on a daily basis. If you can do the vast majority of your computing within that 121 GB limit, then "pure SSD" may very well beat Fusion. In essence would it matter whether you had a 128 GB MBA with a 1 TB external HDD, or a classic Mac Pro with a 128 GB SSD on one sled and a 1 TB HDD on another, or an iMac with a split Fusion drive?

    "Doing a better job than the OS" may be little more than managing your resources wisely. As someone who codes, you're already more knowledgeable about resource management than the vast majority of end users.

    As you admit, living within that limit takes some work. One of the primary premises of Fusion is that there's no work/management required. There certainly is a trade-off with Fusion - performance for convenience and cost.

    Fusion was never sold as a high-performance computing solution. It's been sold as a way for typical users to get near-SSD performance on their desktops at near-HDD prices. Users who have been accumulating data over the course of decades, typically doubling the size of their HDD with each new machine in order to have room for further accumulation.

    The same users who might never take the time to clean out their old junk are also unlikely to manage a split SSD/HDD configuration to run efficiently. Their User folders will be resident on the boot drive, and even if they've moved their iTunes and/or Photos libraries off to the external, Documents, Desktops, and Downloads are going to keep growing until that 121/128 GB limit is reached and the machine grinds to a halt.

    I've said this often, but for the ways I use a computer (which is nothing like the way you use yours), I see little difference in day-to-day performance between my late-2013 Fusion-equipped iMac and my much newer, all-Flash iMac. Most of the time my computers are waiting for me; I spend nearly no time waiting for my computers to do what I've asked. But if I was regularly compiling code and loading VMs... I can see how things might be different.

    For specific professional needs, all-Flash, like a beefier CPU or GPU and more RAM, is a justifiable business expense. And professional or not, if someone can easily afford a Mac with 1 TB or more of Flash (even if it's just for the sake of infrequently-accessed data) I'm not going to tell them they're wasting their money. But for the "typical" budget conscious user in need of large amounts of storage? Fusion remains a very viable option.

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20 January 17, 2016