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. As soon as Apple posts a "Golden Master" build of High Sierra, we will proceed with our last push to update documentation, screenshots, videos, etc. We'll have more documentation and videos coming in the next couple weeks about CCC and APFS, so stay tuned!
Preparing your Mac for the High Sierra upgrade
Before you upgrade to High Sierra, 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, Firewire, 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.
Preparing yourself for the High Sierra upgrade
Perhaps the biggest change in macOS High Sierra is the new filesystem that Apple will be applying to your Mac's SSD/Flash-based storage upon upgrade. This change will be mostly transparent for many users, but if you have several disks, complex partitioning, or if you're just curious how these things work, you might want to take a moment to learn more about this new APFS filesystem. Apple offers a couple helpful APFS-related knowledgebase articles here:
Apple Kbase HT208018: Prepare for APFS in macOS High Sierra
Apple Kbase HT208020: Upgrade macOS on a Mac at your institution
In regard to how CCC will work with your APFS-formatted volumes, this CCC knowledgebase article aims to answer all of the questions you might have on the subject:
Everything you need to know about Carbon Copy Cloner and APFS
If you have additional questions, please let us know! You can reach us right from within CCC — choose "Ask a question" from CCC's Help menu to receive personalized support from our Help Desk.
As with every major, irreversible upgrade, I recommend that any users that rely heavily upon the availability of their Mac for work or other productivity consider waiting a few months 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.
Lastly, I need to give some credit to my team. When Apple introduced Lion six years ago, I was on my own and barely keeping up with support and development. I had great moral support from loyal end users, but the pace was unsustainable. I made a choice then to invest in the company, and now we have a team of six people supporting every aspect of CCC. Four years ago we completely modernized CCC, making it easier to maintain and adapt to Apple's constantly-changing OS. Those investments are really starting to pay dividends, because in just three months, we've managed to pick apart the bootability aspects of the new OS and filesystem and build solid support for it into CCC. I feel like many people look to me as the person behind CCC, but I really want people to know that this isn't possible without all of my teammates. Thanks for making this possible, I'm looking forward to many years ahead of building and supporting a great product!