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macOS High Sierra and APFS: Cautions!

A computer’s file system may not seem to be a terribly interesting topic of discussion, but it becomes interesting when there’s the potential for things to go bump.

So along with the release of the first developer beta of macOS Sierra in June of 2016, Apple included a prerelease version of the Apple File System (APFS), a major update to the previous file system, HFS+, which was released in 1998 as an update to HFS.

Now the file system governs how a computing device, be it a smartphone, a tablet, or a personal computer, reads, writes, catalogs and stores data. If things go wrong with the index or catalog file, you can lose files, or some might end up damaged. While HFS+ worked well enough for tens of millions of Mac users, and hundreds of miles of users of iPhones and iPads, something had to give, so Apple finally developed a modern solution.

So you have such goodies as 64-bit support, robust file encryption, improved performance and efficiency, superior protection from disk catalog damage, and, under some circumstances, near instantaneous duplication of a file.

Obviously Apple proceeded slowly to implement APFS. Last year’s developer version could be installed on Macs with SSDs, but it didn’t support traditional hard drives nor that combo of HDD and SSD, the Fusion drive.

I sort of expected it would be fully implemented with Sierra’s successor, but that’s still a work in progress, which I’ll get to shortly.

But for users of iOS gear, an en masse conversion to APFS occurred virtually without a hitch with the 10.3 update. Hundreds of millions of people had their devices converted in the space of a few days. It was hard to see much of a change. You may have found more free space on our iPhone or iPad, but performance was not significantly different one way or the other. I noticed on my wife’s iPhone 5c that the amount of free space on the 16GB device was little changed. I didn’t bother to compare the before or after on any other device in our household, mostly because I have plenty of free space on my iPhone, and Barbara had no complaints about her iPad.

I suppose you might call it a dry run ahead of the expected conversion on Macs, though I’m sure Apple did a lot of testing before releasing APFS into the wild on such a grand scale. It also made me feel more confident about what might happen on the Mac once High Sierra was released.

With the first macOS High Sierra betas, Apple did provide the choice of converting Fusion drives, but put that to a halt when people ran into troubles. Unfortunately switching back to HFS+ involves invoking some Terminal commands, provided by Apple in a support document to public beta testers, and a full backup, erase and restore.

With the final release of High Sierra, you didn’t have a choice on an SSD. It was automatically convered for better or worse. A regular hard drive can be converted manually in Disk Utility, and I did that on two external drives with mixed results. There is no support for Fusion drives, but that’s promised by Apple in a “future update.”

As I reported yesterday, however, Time Machine evidently doesn’t like APFS. The external drive formatted in APFS was reverted to HFS+ with the first backup. So that, as they say, is that.

Unfortunately, APFS may have other problems. They seem to be related to a few apps, but I’d think that software the follows Apple’s guidelines in reading and writing data ought to work properly with APFS, and if there are problems, they are Apple’s to fix.

On the other hand, if a developer is doing something funky in the way an app talks to the file system, all bets are off.

So far there have been reports that the Unity gaming engine has problems, and a more recent report from AppleInsider mentions APFS issues with AutoCAD 2017 and Adobe Acrobat and Illustrator CC. If it’s a publisher’s issue, there will be updates to recent versions. But if you use an older version of an app, it’s very possible it’ll never work correctly under APFS.

Indeed, I’m going to try my old Adobe CS apps on my 2010 MacBook Pro, whose SSD was converted APFS, to see if any issues arise before I allow my iMac to undergo this conversion.

These reports also raise the possibility that other apps are going to have compatibility issues, but it may again be something Apple can fix for everyone rather than inconvenience customers who, for one reason or another, stick with an older version of an app.

At this point, if you haven’t installed High Sierra yet on a Mac with an SSD, it may be a good idea to check the compatibility of your apps. If you consult our Comments section, you’ll see a post listing a way to hack the installer package to prevent the APFS conversion. It may be the perfect solution, but I won’t endorse something that hasn’t been thoroughly tested. It would be far easier just to hold off for a while. The advantages of High Sierra aren’t so significant that you can’t live without it for a while.

These early release issues may be massaged away with a few maintenance update. There’s already a “Supplemental Update” for High Sierra, which was released Thursday to fix a handful of problems.

I’m still perfectly happy with my decision to install High Sierra. But when or if there’s an update that adds APFS support for Fusion drives, I’ll be gun-shy about converting until I know that my vintage Adobe apps are going to work properly.  I want to avoid the need to subscribe to CS if I can.

Otherwise, I am not changing my qualified recommendation, just adding a few more cautions.