ccc, APFS

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. But today, we're ready.

I didn't make this decision lightly. The scientist in me kicked into gear and I started analyzing some data. I looked at new OS adoption among our user base, I looked at our Help Desk analytics, and I considered the experiences of the users that I've been helping over the past several weeks. As I predicted early in the summer, the APFS conversions have largely gone just fine. This is probably at least partially attributable to Apple backing off on applying the new format to Fusion and AppleRAID devices, but I think some credit to Apple is due here. They pulled this off! The upgrade hasn't been flawless, but based on the feedback that we've received from our users, largely it has gone fine, and anecdotally I think it has gone better than past OS upgrades.

OS adoption among CCC 4 and CCC 5 users

Looking at just the last week, I can see that approximately a quarter of CCC users have upgraded to High Sierra. Sierra remains the dominant OS choice, but I think we'll see that flip in the next three to four weeks; perhaps once the 10.13.1 release is posted.

OS Adoption among CCC 4 and CCC 5 users, second week of October

CCC rises to the APFS challenge

So how did CCC do with the upgrade? In the 16-year history of Mac OS X, High Sierra was the first OS upgrade to introduce a new, bootable filesystem format, so obviously that posed a challenge to the bootable backup solution. In just four months, we picked apart the boot semantics of this new filesystem, added format-agnostic support to CCC 5, tested dozens of source/destination filesystem combinations, assembled numerous pages of support documentation and several new Help videos – CCC was ready for APFS when High Sierra shipped on September 25.

I don't want to be the guy that hoists a "Mission Accomplished" banner too early, but looking back at the last several weeks, we were more prepared for this OS release than any major new OS in the past. We've seen great success making HFS and APFS bootable backups on High Sierra. Our statistics show thousands of confirmed High Sierra bootable backups using both APFS and HFS (roughly 40/60 split), and based on user feedback on our Help Desk, we're seeing very few reports of High Sierra-specific concerns.

Format-agnostic backups

We addressed many of the upgrade-related questions in our Everything you need to know about Carbon Copy Cloner and APFS Knowledge Base article, but one question comes up most frequently: "If my startup disk is APFS now, do I need to erase the backup disk as APFS?" Along the same lines, "If my backup is HFS+ formatted, can I restore that to an APFS disk?" Unlike some other backup solutions, CCC is format-agnostic – CCC can happily accommodate any combination of APFS and HFS that you throw at it. If your pre-High-Sierra backup disk is formatted as HFS+, you can leave it formatted as HFS+ and resume smart updates with Carbon Copy Cloner. Should you need to restore from that backup to your APFS-formatted startup disk in the future, CCC 5 can do that. APFS, HFS, encrypted, not encrypted – whatever format you want on either end of the backup is perfectly fine with CCC and comprehensively tested.

Ongoing support for HFS+ Recovery volumes

We added support for cloning Apple's proprietary "Recovery HD" volume many years ago when it was introduced in OS X Lion. Spanning seven major OSes now, CCC remains the only bootable backup solution that has full support for archiving and creating Apple's Recovery volume on HFS+ formatted volumes. We anticipate that support for HFS+ will be around for a while, so continued support for the HFS+ recovery volume remains part of our comprehensive bootable backup solution.

Go? No go?

Back in June my thoughts about the High Sierra upgrade boiled down to two things: Wait for at least the .1 update, and that a lack of documentation on the new APFS filesystem makes me wary of third-party solutions that leverage its new features (like snapshots). I also suggested waiting to convert to APFS, but that suggestion became moot because conversion is not optional. With a month of public exposure to High Sierra behind us, I feel about the same, though I'm more optimistic now than I was at the beginning of the summer. Once Apple has released the 10.13.1 update, I will be recommending the High Sierra upgrade for anyone that is already interested in making the upgrade.

Some reservations...

I have had some reservations about APFS encryption, but I think the issues we've seen are entirely limited to high-end RAID hardware. If you have RAID storage, I recommend that you consult the hardware vendor to determine if they have tested and can support the use of APFS before applying that format to your own hardware. I had FileVault enabled on my own system prior to upgrading to High Sierra, and now that it is APFS Encrypted, I haven't noticed any problems specific to APFS encryption.

My only other concern relates to third-party SSDs. We haven't received any reports from our own users of any problems with third-party SSDs, however one of our development systems did have an issue back in June with an OWC Aura SSD (right off the bat at Apple's developer conference! It's not easy being an early adopter. And yes, CCC backup to the rescue ?). OWC lists the affected products here, and they report that they're working closely with Apple to resolve the issue. So if you have a third-party SSD in your Mac, do a little bit of research on compatibility before applying the upgrade.


We’re still looking forward to the possibilities of APFS snapshots. We’ve been testing snapshots, but as I said back in June, the documentation for them is still lacking. As soon as we think they’re good to go, you’ll see them in CCC. (But don’t worry, we won’t subject CCC users to beta testing the functionality until it’s good and ready!)