High Sierra, APFS, and your hard drive-equipped Mac

Apple has released High Sierra, a new upgrade to macOS that’s installable on most Macs built since 2009 and 2010. One of the key features of High Sierra is a new file system. There’s a hitch if you’re using a Mac with a hard drive, including Macs with Fusion Drives. File systems aren’t a sexy feature or even a visible one, but the last time the Mac’s file system changed, Bill Clinton was president. So it’s a big deal. Read on for the full story.

Macbook highsierra file system

What’s APFS?

All computing devices rely on a file system to control how your device stores and retrieves data. The file system Apple has used on its device up until recently was called HFS Plus. HFS Plus was introduced in 1998, updating an earlier file system (plain old HFS) that had already been around for 13 years. So the Mac – and by extension, the iPhone, iPad, iPod touch and other Apple devices – used a file system that was 30 years old.

Times change, and so does technology – rapidly. Storage needs have increased exponentially HFS  debuted in 1985. At the time HFS was first introduced, a 20 MB hard drive was astonishingly big. Now devices in your pocket can hold 128 GB or more.

What’s more, there’s been a sea change in how storage works. When HFS Plus was introduced floppy disks and spinning hard drives were the way most devices stored data. Floppy disks are a historical relic, and hard drives are headed that way too. Now devices across Apple’s product like rely on flash storage – writing data to silicon instead of to the surface of a spinning disk.

Apple needed to future-proof its core file system technology, and needed to adapt it to the changing needs of flash storage. APFS was the solution. APFS employs advanced data integrity features to make sure your data is safe. It’s also tremendously more efficient when it comes to copying files and folders – you’ll see almost instant operations.

APFS is very much an “under the hood” change. You won’t notice anything visibly different, but the way in which your Mac stores files and interacts with its storage system are more efficient and better suited for the future than how it’s worked up until now.

APFS was rolled out to iPhone and iPad users earlier this year with the release of iOS 10.3. With the general release of High Sierra for the Mac, APFS has come to Macs too.

Auto-Conversion to APFS for Flash-Only Macs

If you’re using a Mac equipped with all-flash storage – a Retina MacBook Pro, for example, or a MacBook Air, MacBook, a 2013 or later MacBook, some Mac mini and iMac models – the conversion to APFS will be automatic when you first install High Sierra. The conversion to APFS even happens if you’ve upgraded your Mac with some Solid State Drives (SSDs). I put a third-party SSD in my Mac mini, and High Sierra’s installer managed the conversion to APFS without complaint.

If you’re using a Mac with a spinning hard drive, or Apple’s “Fusion Drive” equipped models, High Sierra will not automatically convert your device to APFS. Apple decided before High Sierra’s release to automatically convert only those Macs powered by pure flash storage. In fact, beta testers who have made the conversion on their hard drive-equipped Macs are required to reformat them to HFS Plus to install the general release.

APFS Coming Soon for Everyone Else

Apple has also said, unequivocally, that APFS will be coming to hard drive-equipped Macs in a future High Sierra update. In announcing High Sierra’s release, Apple said, “APFS currently supports every Mac with all‑flash internal storage — support for Fusion and HDD Mac systems will be available in a future update.”

Apple hasn’t explained the delay. I’ve heard through the grapevine that a certain number of hard drive-equipped Macs were failing the installer’s initial conversion. If that’s the case, Apple’s decision to delay APFS conversion for those Macs is prudent. No one wants to install software that could potentially leave our Mac as a doorstop.

As always, having a backup and recovery strategy is important. Flash-equipped or not, make sure your Mac is backed up. For more on prepping your Mac for the switch to High Sierra, read my Upgrade Tips for High Sierra, and feel free to let me know if you have any comments or questions.










10 thoughts on “High Sierra, APFS, and your hard drive-equipped Mac

  1. Hello, Peter,

    I wonder if you have a word of advice. I installed Office 2016 on my Mac Pro, however, I cannot find it. I see it in the hard disk, but have not way of activating it. I tried different troubleshooting tips I found in in the internet, but nothing seems to work.

    Thank you,


    PS. I tried to leave this in your Contact Me section, but it wouldn’t validate the text below.

  2. Hi, Ines. If Microsoft Office 2016 installed on your Mac like it did on mine, you should see the individual office apps inside your Applications folder. Launching any one of them should commence the activation process if they’re not already activated.

  3. Hey Peter: Great following you on your blog. Religiously listened to the “Angry Mac B – – – – – ds” in years past.

    I’ve not received any difinitive answers from Apple tech support on these questions…
    -Have a 2013 iMac with a 1TB internal spindle drive. Had an interal OWC SSD installed in the iMac as my boot drive; also houses my apps. The 1TB spindle is now relegated to storage. IF I upgrade to High Sierra, will the iMac treat the spindle drive with respect; read-write etc.?
    -I also have a very recent 2017 Macbook Pro. High Sierra will function but,
    -I make bootable backups of my boot drives on both machines daily, using carbon copy cloaner. IF my cloaner drives are spindle drives, but the Mac-native interal is a High Sierra SSD, what happens to the integrity of my boot clone?
    -Similar scenario, if my CCC Clone is an external SSD, will that make the external SSD Clone a functioning backup?
    -Same question(s) apply to my Time Machine backups on both the iMac & MBPro. My time machine drives are spindle externals. What happens to the integrity of the time machine backup interacting with High Sierra?

    I’ve put these questions to Apple Tech and they have zero definitive answers; very non-committal.

  4. Chris:

    I would think Bombich Software might have something to say on the cloning issue. Bombich will have a better sense for you about how their clone software interoperates with APFS and HFS+ and cloning.

    Time Machine and High Sierra: See this Apple tech note.

  5. I installed High Sierra on my late 2012 27” iMac. External HDD problems: Seems to mount, but cannot read or write (HFS+) Four volumes on 3 HDDs in 2 enclosures, all fail. Also a FAT32 thumb drive doesn’t work. The internal startup 6TB HFS+ HDD seems to work. I can copy from my external HFS+ TimeMachine to the internal drive, but it only made one new backup since the OS upgrade, and will not make more.

    All of these drives function normally on my “early 2015” MacBook Air, running on High Sierra.

    Any ideas?

  6. I have a MBP mid 2012 with HDD. I plan to change the HDD to a SSD, but wonder what will be the best practice to make this upgrade? If it is possible to clone the SSD from the HDD, I feel this would be the easiest path, but I am not sure if this can be done as I believe it is not possible to keep the HFS+ on the SSD. The other option I see is making a bootable USB stick with High Sierra and fresh install the OS after formatting the SSD to APFS, and installing programs and files from a TimeMachine backup. Any suggestions, experiences or comments are welcome.

  7. Kjell:

    My last HDD to SSD conversion was a 2014 Mac mini. I did this over the summer before High Sierra was released. I put the SSD in a USB sled, formatted it (for HFS+ at the time, YMMV), installed macOS from the Recovery partition, then restored from a Time Machine backup. It went flawlessly.

    That system upgraded to High Sierra after it was released, and the High Sierra installer managed the HFS+ to APFS conversion without skipping a beat.

  8. Coming to this a bit late (!) but would greatly appreciate your advice. I’m trying to move from an iMac (still running Sierra, on a spinning drive) to one running Mojave (on an Fusion Drive). I was planning to use SuperDuper, booting from my Sierra Clone (external drive) but when I do the internal Fusion Drive is not accessible. Would Target Disk Mode work? I’m reluctant to upgrade the old machine from Sierra to Mojave: if anything goes wrong I have no ‘backup’ and I suspect many of my old 32-bit apps won’t work in the new environment. A bit stumped by APFS. Can/should I remove it from the Fusion Drive and clone away? All advice gratefully received.

  9. I just want to know what hard drive I can get with ‘plug and play’ feature. I am not a techie and don’t want to be one. I have 2017 iMac which is only used for photography, nothing else. A hard drive is as high tech as I want to be.

  10. Literally any USB hard drive you might buy is plug-and-play, though you may have to reformat it for Mac using Disk Utility, which comes on your Mac.

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