Executive Summary

Beta 5 is linked at the bottom of the post: we now copy Recovery volumes from both HFS+ and APFS sources to APFS, and "stash" recovery on HFS+ destinations for restoration to APFS if needed.

Details, Details!

Before the advent of APFS, volumes were rigid elements created by physically partitioning a drive, logically erecting barriers between fixed areas of storage. While in later versions of macOS those barriers could sometimes be moved by the command-line diskutil, that functionality was not exposed in the GUI Disk Utility until relatively recently, and was prone to failure.

Even then, adding, resizing and removing partitions was more convenient and accessible...but relatively fragile. Reliable, extensive partitioning (with a friendly interface) was only available in 3rd party tools like iPartition, because it was able to physically relocate data blocks, change partition schemes, etc. The inherent rigidity of the layout of HFS+, even after the introduction of the intermediate-layer CoreStorage setup, got in the way of reliable volume creation and resizing, making the process risky.

Casiotone Nation

The design of APFS changes and improves all of that. Volumes inside an APFS container aren’t defined by rigid barriers, and their storage doesn’t have to be contiguous. All of the volumes in a given APFS container are extremely flexible and share a common free storage pool managed by the container itself. Creating and deleting partitions is a simple and safe operation. There's no need to create images to try to maximize storage efficiency on a drive, or to store three backups on a given drive: you just add new partitions, and they do what you'd expect. Failure is quite rare and for typically obvious reasons.

The Past is Prologue

When Apple got rid of CDs and switched to Recovery it was, in many ways, a step back. Reliable, immediately accessible, archivable media was replaced by a hidden volume on a drive that could fail. Even though Internet Recovery, an EFI-based failsafe, provided a backstop, it took a long time (and required internet access) when things went really wrong.

Save for bootable encrypted volumes, though, the Recovery volume was a nice thing to have on a backup volume, but not a necessary one. While it wasn’t terribly challenging to copy a Recovery volume, creating the partition for it, given diskutil’s capabilities, was risky. And its contents were also undocumented, even if relatively consistent from release to release.

Given Apple could recreate the Recovery volume during a macOS reinstall (a time consuming but easy operation that put a fresh OS under existing applications and data), and the fact that it wasn't needed for startup or restore, we decided to take a more conservative, safer approach and not copy Recovery.

Not because we couldn’t. But because we didn’t think we should, given the risks involved.

#It Gets Better

The introduction of APFS allowed us to revisit that decision. Because its more flexible volume creation is low-impact, the risks inherent in adding and managing the Recovery volume itself are minimal. Recovery now has its own special, documented “Role” within the APFS container, and its contents follow the pattern established for Preboot. Even encryption is done differently: it's properly managed in Preboot, which can be created and updated by a documented system tool, provided by Apple, further ensuring proper operation and compatibility as Apple makes changes and modifies requirements.

After carefully evaluating the new support and determining there were minimal risks, we decided that we could safely copy and manage Recovery for APFS containers, whether copied from APFS or HFS+ sources. And so we do.

That means we still don't create a Recovery volume on an HFS+ volume for the reasons above...but we can copy from an HFS+ volume to an APFS volume and properly copy its recovery to APFS (since that's as safe as APFS to APFS).

If you're copying HFS+ or APFS to an HFS+ device, we still work when restoring to APFS: we automatically create a Recovery “stash” on an HFS+ volume, and can restore it to APFS when necessary.

Your Well-Earned Reward

While the details above are a bit complicated, the best part is that, as with most other aspects of SuperDuper!, there’s nothing you need to do. The details are handled for you. It just works.

In the end, that’s our goal, and our slogan: Heroic System Recovery for Mere Mortals. We hope you agree.

SuperDuper! 3.0 B5.1


The above is the 2nd post of Beta 5 (I called it Beta 5.1 but the version is the same). The first Beta 5 had a bug in it that caused temporary folder cleanup to fail.

This got through regression because we had tested against a number of bootable volume cases without checking the startup volume on the High Sierra test system itself (as opposed to the thumdrives, etc, that we've got for the various disk cases we handle). We tend not to run that every time because the variations (Erase, Smart Update, etc) take much longer with a huge drive. Alas, the startup volume is a different case...and we missed it.

Needless to say, that case is now checked even though it's slow (vs only during "dogfood" daily-build backup runs).

Ah, public betas This kind of stuff is OK when it's all internal. Sorry about that!