What Is APFS?

Apple's new file system is a big part of the new macOS High Sierra and iOS 11. What is a file system and how is APFS different than the old Apple file system? What advantages will APFS bring to our Apple devices? Which devices will this affect and when? How will we upgrade our Macs, iPhones and iPads to APFS?

Video Transcript
So with the announcement of Mac OS High Sierra and iOS 11 comes a big change under the hood for all of our Apple devices. It's called Apple File System or APFS for short.

So what is a File System? Well a File System is how your computer stores files and other data on the hard drive or other storage system. Now all these details are things we don't have to worry about as users. But it has to keep them organized. It has to know where files are, where the data for the files is kept on the drive. It has to move them around and take care of all sorts of things like creating new files, deleting files, copying files, duplicating files. All those details are part of the file system.

So before, and for many years, Apple had a file system called Mac OS Extended or HFS+. This was the file system used on all Macs and was also used in iOS, on the Apple Watch, and even Apple TV. It worked great and it was generally pretty fast. Now it's different than a system used say on a windows machine. That's why a lot of times you had to format a drive with a windows format so it could be read on windows and the Mac could also read that format. But the native Mac format, Mac OS Extended, is the one that say your boot up drive would use and your Time Machine drive would use.

Now we're going to change from using this Apple Mac OS Extended format to APFS. So what makes APFS better. Well there's several different things that it brings. First and foremost is speed. It's faster. So it's a more modern system. As you can imagine a system developed in 1998 isn't very good with handling things like solid state drive, flash memory in phones, and things like that. This is very optimized and should be faster for all things you need to do including even booting up your device.

There's a special thing in APFS that allows you to clone files faster. So say you have a huge video file and you want to make a copy of it. You can duplicate it and it will happen instantly even though it's a huge file because it actually just stores the data once and points to the same file for both copies. As you make changes it records the differences between those files, not necessarily making an entire other file and having everything copied there.

There's also something called Snapshots. This should help a lot with backups. Snapshots are a way for to quickly create read only copies basically saving the entire state of the drive very fast.

Another thing that APFS handles very well is encryption. So it's supported natively. With the old operating file system you had to, you know, had to basically save an encrypted file. Which is just a normal file. But this is handled much more directly in APFS.

There's also some crash protection. It's going to write files in such a way that's going to avoid corruption. So if you're writing a big file and say you loose power or something like that it's less likely to cause a problem under APFS than it was under the old file system.

Space sharing is another advantage. You'll be able to have a drive that's partitioned say into two or three different volumes. They'll be able to share the same free space. So you should be able to do some interesting things having a big drive partitioned and not having to decide exactly how much goes with each partition right off the bat.

Where are we going to see the new APFS. Well pretty much everywhere in the Apple world. Because we're going to get it with the new version of Mac OS called High Sierra. We're going to get it with iOS 11 and we're going to get it on the new versions of the operating systems for both the Apple TV and the Apple Watch. So they're going to switch the entire Apple world over to APFS.

How is this going to happen? Well, it's going to happen automatically. When you install High Sierra or iOS 11 part of the installation process will be converting the drive in place to APFS. It should just happen automatically and seamlessly. Of course any time you do something as big as an upgrade to a new operating system you should make sure your backup is all good and working first. So there really is no danger in doing it this way. And supposedly everything is going pretty smoothly with beta conversions.

How about backward compatibility? So you're in the new version of the file system but now you have drives that are using the old one. Well, you'll still be able to read those old drives just fine. But with the new drives how about if you have an old Mac, an old Mac that's running say El Capitan. Will it be able to read new drives formatted in APFS? No it won't. Now if they are Mac OS Sierra computers they will because Sierra supports APFS. It just didn't implement it as the primary file system.

So anything you've got that runs Sierra will still be able to access new drives using APFS. Any new computer you've got using APFS should still be able to access anything you have formatted in an old format say on an old external drive with an archive.

So when is this going to happen? Well, it will happen with the release of High Sierra and with iOS 11 which will happen in the Fall. In the past Apple has had the releases right around September 30th, October 1st. We just don't know for sure when the date will be. But when you upgrade to these operating systems that's when you'll be switched over to APFS.

Comments: 14 Responses to “What Is APFS?”

    Douglas Brace
    6/19/17 @ 11:39 am

    APFS is the file system used in iOS 10.3 so it was used before iOS 11.

    6/19/17 @ 11:45 am

    Douglas: Good point. We already have this on iOS as of March.

    6/22/17 @ 10:01 am

    Hi Gary, I’ve read somewhere that MS Office 2011 will not be compatible with High Sierra. Is this true, will MS make an update or will I have to give up MS Office altogether and convert all my MS file to Pages and Numbers. I am a commercial realtor and I have some fairly complex Excel files and I don’t want to pay for another Office.

    6/22/17 @ 10:04 am

    Jean-Marc: Where did you read that? And what difference does it make — Microsoft has come out with several versions of office since 2011. Why not use the latest one?

    Gordon Stallings
    6/22/17 @ 12:39 pm

    For the Realtor, Open Office is compatible with MS Office and the spreadsheets work the same. Since I’m using Open Office, I’ll be careful about upgrading to APFS until I’m sure it’ll all work properly. And by the way, will thumb drives formatted with APFS be compatible with Windows machines? Or do I still need to use FAT?

    6/22/17 @ 12:43 pm

    Gordon: I doubt Windows machines will be able to read drives using APFS since they can’t even read the current Apple format that has been around for so many years.

    6/23/17 @ 5:51 am

    How can copying a file be instantaneous? It must be different from creating just an alias, no? Otherwise, when deleting the original file, everything will be gone. Please explain.

    6/23/17 @ 7:08 am

    Theo: When you copy the file, a “clone” is created. So put it simply, the data is the same and not duplicated, but a new pointer is created to that same data. Delete the first file and the pointer to the data is deleted, but the data remains. Delete the second file and that pointer is deleted, nothing else points to the data, so the data is no longer needed at that point either. When you make changes, the changes are recorded, not an entirely new file.

    Pete Schirling
    6/24/17 @ 2:06 am

    1. How will TimeMachine and sparsebundle files be effected by APFS?
    2. I use an external drive as a secondary backup (especially when traveling). It is My Passport for MAC. What effect will APFS have on it?

    Thank you.

    Donald Kryzak
    6/24/17 @ 6:12 am

    I have a portable hard drive with thousands of photos on it and the drive is in Mac OS Extended (Journaled) format. How can I preserve those photos?

    6/24/17 @ 6:58 am

    Donald: There’s nothing you need to do. Macs will still be able to read Mac OS Extended format drives. It is just that APFS will become the new default. Of course, make sure you are backing up those photos somewhere — don’t make that one drive the only place they exist!

    6/24/17 @ 7:00 am

    Pete: Time Machine will be greatly improved by the speed of APFS. Not sure what you mean by how this will effect sparse bundles, I’d expect they’s be faster and better too — or something like it. Your current externals are fine as Macs will still be able to work with MacOS Extended format, it is just that APFS will be the default.

    6/24/17 @ 8:36 am

    Hi Gary! Good video!
    With APFS, does this mean that I won’t need Tuxera NTFS anymore to write to an NTFS formatted drive?
    Thanks in advance.

    6/24/17 @ 11:18 am

    Robert: APFS doesn’t change anything in that regard. You would still need special software to access unsupported drive formats like NTFS.

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