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Mike's picture by Mike | September 12, 2019

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.

Test Setup

I wanted to see how an APFS formatted volume performs over time under "normal" usage conditions and how that compares to an HFS+ formatted volume under the exact same conditions. To do this, I had to set up a simulation that would produce identical changes on two volumes to allow for a consistent, objective analysis of the filesystem performance. When I refer to "filesystem performance," I'm specifically referring to how long it takes the filesystem to do transactional tasks. Read and write performance depends almost entirely on the speed of the media, so I wanted to factor that out of my tests. Enumerating the contents of the filesystem is a good exercise of filesystem transactional performance, so I decided to test the enumeration of 1 million files on each an APFS and HFS+ filesystem over a period of simulated modifications to the filesystem.

The destination device in these tests is a 2TB Western Digital MyBook Duo split into two equal partitions. One partition is formatted HFS+, the other APFS. Spotlight was disabled on both volumes. Snapshot support and APFS defragmentation were varied in different tests to determine whether they had any effect on filesystem performance.

The number of files in the file set is constant – 1 million files, 111,000 directories (files nested three directories deep). To make the simulation closer to real-life, the file size distribution roughly follows 1/x2 – it’s weighted more heavily towards smaller files. Each individual file size is determined randomly, but in a pattern that follows that size distribution histogram. Average data set size is ~18GB. Max file size is 20GB. The... Read More

Mike's picture by Mike | June 6, 2019

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


What an exciting week! Once again this year our team was graced with a WWDC "Golden Ticket". Last year I got to go, but this year Peter from our Development team went and had the opportunity to speak directly with Apple's File Systems team about the upcoming changes to APFS. Among the new announcements this year is the introduction of a read-only system volume on macOS Catalina. From the moment that Apple announced APFS, I anticipated exactly this sort of setup – user data on one volume, macOS on another – complete separation, absolute protection for the system. Apple has implemented this in a manner that will be (almost) completely transparent to the end user, and so far, I'm pretty stoked about how all of this works.

What implications does the read-only system volume have for CCC backups?

In the Finder you'll only see one volume that represents your startup disk and it will appear as if everything is on that single volume. In reality, the startup disk that you see in the Finder is the read-only system volume and doesn't have any of your data on it; the "Data" volume is separate and hidden. CCC will have to find that hidden volume (don't worry, I know where to look :-) and back up its contents alongside the system volume. The current version of CCC can't do that, of course, it knows nothing about APFS volume groups. We're adding that functionality right now, though, and we'll be hard at work over the summer on some new documentation that will help explain everything that you're seeing (or not seeing!) on the newOS.

What are the implications for my backup disk?

Allow me to be the first to say it: stick a fork in it, HFS is done. HFS simply won't work for making a backup of a Catalina system volume, so in the near future, we're going to drop support for backing up macOS (Catalina and later) to HFS+ formatted volumes. We plan to make this as easy as possible for you, though, so don't go out of your way to get ready for this. My goal is to make this transition as simple as possible for you and your backups.

If you're testing Apple's new OS already, stay tuned for another CCC beta release that will start to add support for the new features of macOS Catalina.

Sarah's picture by Sarah | December 22, 2018

We will be closed December 24 and remain closed December 25 to spend the holidays with our families. We will also be closed December 31 through January 1. 

Limited staff are available to respond to customer requests until January 2. We appreciate your patience if it takes a bit longer for us to respond than is typical.

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Mike's picture by Mike | September 17, 2018

In a delightfully predictable manner, Apple announced last Wednesday that macOS Mojave will be available on the Mac App Store on September 24. From the moment that Apple introduced Mojave to developers in June, we've been putting it through its paces to see what we can expect when Mac users apply the upgrade this Fall, and to get CCC 5 qualified on this new OS. We're happy to announce that CCC 5.1.5, available today, is fully qualified on macOS Mojave.

Getting Ready to Upgrade to Mojave

I say this every year, but it's worth repeating — before you upgrade to Mojave, it is imperative to understand that downgrading to your previous OS will be impossible without a bootable backup of the previous OS. Before you apply the upgrade, we recommend that you establish a bootable backup of your current OS on an external USB or Thunderbolt hard drive, then verify that you can boot your Mac from that backup disk. Before you pull the trigger on the upgrade, detach that external disk from your Mac and set it aside.

For more detailed advice on preparing for the upgrade and instructions on how to downgrade, check out this CCC knowledgebase article:

Best practices for updating your Mac's OS

The one thing I would add to the "getting ready" check list is simply a heads up to a behavior that we discovered in the upgrade process: When you apply the upgrade, the macOS Installer may delete snapshots from your startup disk. If you have been enjoying CCC's new snapshot support, be prepared to lose those snapshots on your startup disk. This isn't a showstopper, but it did come as a surprise.

When should I upgrade?

As with every major upgrade, I recommend that any users that rely heavily upon the availability of their Mac for work or other productivity consider waiting for a few OS updates before making the upgrade. The early releases are exciting, but with any excitement there's usually a bit of risk. Early adopters will surely find some shortcomings and bugs which will be resolved in the next few months with minor OS updates. Does this upgrade fix a problem that causes me daily grief? Will this upgrade improve my productivity or security, outweighing the time I may have to invest in fixing early-adopter problems? Those are the key questions I ask myself before applying any upgrade.

New Privacy Controls – Mojave adds some busy work

By default, Mojave will deny all non-Apple applications access to private data (Mail, Messages, Safari History, etc.). For anybody that bathes their Mac in a sea of malware, this will be a welcome default. For the rest of us that use a pretty straightforward, curated list... Read More

Mike's picture by Mike | March 30, 2018

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.

Versioned backups with APFS Snapshots

CCC 5.1 offers support for point-in-time restores by leveraging the snapshot feature of Apple's new APFS filesystem. CCC's SafetyNet feature offered similar functionality to this in the past, but snapshots take it to a new level, allowing you to do things like restore a previous version of the OS and older versions of your Photos library.

CCC is also the first comprehensive snapshot management utility for macOS. Browsing the contents of any snapshot is just a click away, and should you want to delete a specific snapshot (whether created by CCC or Time Machine), just select it and press the Delete key. How much space are those snapshots consuming? CCC can tell you that. No other utility offers this much insight into your APFS volumes' snapshots!

CCC 5.1 introduces comprehensive support for APFS snapshots

CCC 5.1 is currently available for beta testing. If you're the beta-software-testing type, check the "Inform me of beta updates" box in the Software Update section of CCC's Preferences window, then click the "Check for updates now" button if you would like to try it out.

Learn more about how you can add snapshot support to your backup strategy

Read-only snapshots offer great protection against ransomware

Snapshots are read-only copies of your volume. Not only is it impossible to modify the content of those snapshots, but it’s also not possible to delete those snapshots without a special entitlement granted by Apple. What that means is that malware and ransomware can't delete your snapshots. So if you were somehow affected by ransomware and it started encrypting your files, you could remove the ransomware, then restore your files from the snapshot. CCC backups could literally save you thousands of dollars!

What can I do to make sure my backup strategy is going to be effective?

I have four general tips: make backups to a locally-attached hard drive, keep it current, keep it encrypted, keep it unmounted.

Make backups to a locally-attached hard drive

NAS backups sound convenient and Cloud backup is the buzz, but when it comes down to actually using your... Read More