APFS

A bug in macOS 10.15.5 impacts bootable backups, but we've got you covered

Update (July 16, 2020): Apple fixed the underlying OS issue described below in macOS 10.15.6, and the CCC 5.1.20 update puts our workaround on the back burner. Every challenge opens up new opportunities, and that's actually how we're seeing this incident in retrospect. Rather than just hoping for a fix, we invested in a solution, and that solution puts us in a solid position for the next major OS.

Cloning Catalina with Carbon Copy Cloner

We posted our Catalina-certified build of CCC way back in August, so the last few weeks have been eerily calm. Now that Apple has made the OS release schedule so consistent, we find this time of year to be a lot less stressful by simply being ready for it, on time. Since about Catalina Beta 9, the OS has been feeling pretty polished and ready for prime time. I think I have just one gripe with Catalina — Spotlight is so persistently annoying when it prevents volume unmount requests!

An analysis of APFS enumeration performance on rotational hard drives

Update March 30, 2020: Perhaps this is exacerbated by changes in macOS Catalina, but we have found that APFS performance on the slower 5400RPM HDDs to be unacceptably poor. Stall analysis indicates that APFS gets bogged down when renaming files, especially in folders with many other files. We do not recommend using APFS on the slower 2.5" "slim" HDDs.


My APFS-formatted rotational disks have always felt slower than when they were HFS+ formatted. The speed of copying files to them felt about the same, but slogging through folders in the Finder was taking a lot longer. At first I shrugged it off to the filesystem being new; "It just needs some tuning, it will come along." But that performance hasn't come along, and after running some tests and collecting a lot more data, I'm convinced that Apple made a fundamental design choice in APFS that makes its performance worse than HFS+ on rotational disks. Performance starts out at a significant deficit to HFS+ (OS X Extended) and declines linearly as you add files to the volume.

The rest of this article is fairly technical, here are the key takeaways:

  • Enumerating an APFS filesystem on a traditional HDD (rotational disk) will take 3-20X longer than HFS+ on the same hardware.
  • This performance difference is most noticeable on a macOS startup disk that is (or includes) a rotational disk.
  • If Apple doesn't make some concessions in the APFS filesystem to accommodate the slower seek performance of HDD devices, then a rotational device will never be able to provide acceptable performance as a production macOS startup disk.

Catalina, Read-only System Volume, and HFS is getting out of the system business

Update July 18, 2019: CCC 5.1.10-b3 is now available and addresses the bulk of the changes required for supporting macOS Catalina.

Building Better Backups with Carbon Copy Cloner

On the eve of World Backup Day and with stories like the Atlanta ransomware attack still in the news, now is a great time to revisit your backup strategy. It's also a great time for us to announce some great new features that we're getting ready to deliver as a free update to CCC 5 users – features that will help you improve your defenses against ransomware and malware.

macOS may lose data on APFS-formatted disk images

Update September 24, 2018: This issue is resolved on macOS Mojave.

Update March 30, 2018: This issue persists on macOS 10.13.4 (17E199)


This week we reported to Apple a serious flaw in macOS that can lead to data loss when using an APFS-formatted disk image. Until Apple issues a macOS update that resolves this problem, we're dropping support for APFS-formatted disk images.

Evaluating the High Sierra Upgrade

Well, I did it. I know that I've told many people I'd be waiting until Thanksgiving to apply the High Sierra upgrade to my own production machine, but after some reflection this week, I decided that High Sierra was ready for me, and that I was ready for High Sierra. I've always been decidedly anti-upgrade when it comes to my own production system. Upgrades tend to break things, and I just can't afford downtime on my laptop. High Sierra and the APFS transition, to me, was a potential double-whammy for breaking things, so I was bearish on this upgrade in particular.

Think twice before encrypting your HFS+ volumes on High Sierra

One of our users made a startling discovery this week after upgrading to High Sierra. He had an HFS+ formatted 16TB RAID device, and had always intended to enable encryption on that volume. There's no OS on it, so he simply right-clicked on the volume in the Finder and chose the option to encrypt it:

Screenshot of Finder contextual menu showing encryption option

This is an easy way to enable encryption on a volume: plug in a password, verify, add a hint, done!

Resuming your bootable backups after upgrading to High Sierra

The time for betas is over! High Sierra is here. APFS is here. We're ready for both, and we've got you covered. APFS, HFS, encrypted, not encrypted, FileVault – whatever your source or destination, we support all of these combinations in CCC 5. We've tested so many different scenarios, we put the results into a chart to keep track of them.

Preparing for the upgrade to macOS High Sierra

On Tuesday Apple announced the release date for macOS High Sierra – we can expect to see it on the App Store on September 25. We've been busy testing High Sierra over the summer, and I'm happy to say that we're ready for it. We've posted an update to CCC 4 that fixes a couple cosmetic High-Sierra-specific issues, and we're preparing to release an update to CCC 5 with the same fixes, plus more improvements that are specific to High Sierra.