High Sierra on Fusion Drive

Discussion in 'iMac' started by Macintosh1984, Nov 10, 2017.

  1. Macintosh1984 macrumors regular

    Dec 15, 2012
    Hi! Is it possible install High Sierra on a Fusion Drive disabling APFS, so having the old HFS+ system? When installing High Sierra, there is a chekbox to uncheck?

    Do yuo think that when APFS came out to Fusion Drive (when?), we need to reformat again the Mac or HFS+ to APFS will be a normal upgrade without data lose?

    Or do you think it is better to separate my hard drive, 1 partition SSD + 1 normal?
  2. nambuccaheadsau macrumors 65816


    Oct 19, 2007
    Nambucca Heads Australia
    Estimated to be in the New Year with about update OS X.13.3. Suggest just wait.
  3. Macintosh1984, Nov 10, 2017
    Last edited: Nov 10, 2017

    Macintosh1984 thread starter macrumors regular

    Dec 15, 2012
    But now I can install High Sierra with HFS+ or the new system is completely incompatible with Fusion Drive?

    Or do you recommend to defuse "Fusion Drive".
  4. xgman macrumors 601


    Aug 6, 2007
    I think HS will automatically see you have a Fusion Drive and install as HFS+ anyway.
  5. Macintosh1984 thread starter macrumors regular

    Dec 15, 2012
    I need your advice:

    1) install HS as HFS+;
    2) "defuse" Fusion Drive so HS is on SSD with APFS, the other normal disk will be HFS+ partition;
    3) wait HS with APFS Fusion Drive compatible.

    I would like to choose 2), is it possible? Do you recommend it? It boost Mac? Defusing invalidates the warranty? Defusing is against Apple rules?
  6. cynics macrumors G4

    Jan 8, 2012
    Isolating the drives wont void your hardware warranty.

    If you don't mind me asking what is the reason for you wanting to unfuse the FD?

    Personally without a specific reason I don't recommend it. Corestorage for the FD operates on a block level so its capable of more effectively and efficiently utilizing the SSD. This doesn't mean it always will however it can fit a lot more onto the SSD then you can. To simplify that, it can move portions of programs and even singular files to the SSD which the user can't do. So if you only use 50% of all your programs capabilities (think of a features in programs you never mess with) it could in theory put twice as many programs on the SSD (50% of them) as you can manually.

    With APFS the FD algorithms are supposedly getting even more intelligent.

    Again though not saying unfusing the drive is a bad idea but many people are given the impression it comes without compromise.
  7. Macintosh1984 thread starter macrumors regular

    Dec 15, 2012
    If I defuse Fusion Drive, I can install HS with the new filesystem right now.

    I think that a pure SSD is better at all. I think I can manage the SSD and the mechanical HD manually and correctly, to get the maximum of the set-ups without the operation of automatisms that in theory could sometimes make slowdowns on Fusion Drive, !'m wrong?
  8. cynics macrumors G4

    Jan 8, 2012
    Yes and no. Technically you can't manage the data the same way the FD can. It operates on a block level (of data) while you deal with files.

    For example say you use photoshop and its a 1000mb program, however you dont do anything advance in it. The FD could move 500mb (just an example) of the program you dont use onto the HDD saving you 500mb of SSD space. You can't manually split a program like that.

    Another example, say you repeated watch the first half of a movie you have downloaded on MP4. It could move the that first half of the file to the SSD and the part you never watch to the HDD. Again something you can't do.

    However if all your stuff fits on the SSD and you just use the HDD for media (or nothing) then unfusing it would probably be better. You wont have to deal with the initial slow down while it learns either.

    Again, I'm not saying the idea of unfusing is bad, just there are benefits of a FD too. In my experience with a 2tb FD I ended up preferring to let it handle where the data ended up. While I didn't particular like the idea of a commonly listen to MP3 making its way onto the SSD if I listen to it enough it made sense to have fast access too it. I also didn't like the idea of portions of my commonly used apps ending up on the HDD because I never used them, because I felt that I might one day....I never did....
  9. Fishrrman macrumors G5


    Feb 20, 2009

    You can "de-fuse" the fusion drive if you wish.
    No one's going to arrest you for doing so.
    Actually, the iMac will probably run faster if you do that.
    And it will KEEP RUNNING FAST because the de-fused SSD will always run at its highest speed.

    You really should do this ONLY if you have the 2tb or 3tb fusion drive.
    The SSD portion of the 1tb fusion drive is very small (32gb) and probably wouldn't work well as a "standalone boot drive".

    Once the drives are de-fused, you can install APFS on BOTH of them.

    I see no great shakes to having APFS right now.
    It seems to be causing problems for some folks and outright havoc for others.
    I have no intention of using APFS at any time in the near future.
    I'll migrate to it only when no other course of action is possible.

    Some more thoughts:

    BEFORE you do ANYTHING above, you need to do this:
    1. Get an external drive large enough to hold your existing installation
    2. Get either CarbonCopyCloner or SuperDuper (both are FREE to download and use for 30 days)
    3. Create a BOOTABLE CLONED BACKUP of your current fusion drive.
    This gives you "an easy way back" if something goes wrong.
    If you don't do this, you can still "get back", but it's NOT going to be easy.

    AFTER you do the above, do this:
    1. Get a USB flash drive 16gb or larger
    2. Get ONE of the following: "Boot Buddy" or "DiskMaker X" or "Install Disk Creator"
    3. Use one of the above (free) apps to create a bootable USB flash drive with the High Sierra installer on it.
    4. Boot from the flash drive and do the install that way.
    Much better chance of success if you take this route.
  10. Macintosh1984 thread starter macrumors regular

    Dec 15, 2012
    That's right!

    I think I can get everything I use in my SSD, the rest that does not require speed, stored on normal HD.
    --- Post Merged, Nov 11, 2017 ---
    My Fusion Drive have 120,99 GB SSD!

    Why you don't what use APFS? What problem you hear?

    Why "Once the drives are de-fused, you can install APFS on BOTH of them"? APFS seems is only for SSD!
  11. Anonymous Freak macrumors 603

    Anonymous Freak

    Dec 12, 2002
    Just keep Fusion drive.

    Upgrade to High Sierra, keeping HFS+.

    When Apple enables APFS for Fusion Drives, I'm sure there will be a way to upgrade-in-place, much as SSDs do during the High Sierra upgrade.

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