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tl;dr - new beta release (B5) now available. Very minor changes, including additional prompts for old licenses on Apple silicon. Download away.

Download SuperDuper! v3.5 B5

Signposting

So, B4's rollout went well, with only a few people accusing us of trying to "put one over" on people by invalidating licenses.

Honestly, that wasn't the intent. If we wanted to invalidate licenses and force people to buy new ones, we would have just done so.

Unfortunately, those users didn't read the post that explained the situation, and so we've added another notification about old license use at startup. Hopefully that'll help guide people either to Rosetta or a new license with less mystery and intrigue.

Disk...full?

Somehow, one of the sections of the What's going to happen? section that pointed out when a source might not fit on the destination seemed to be missing.

After an investigation, including combing the beaches to see if it had just headed to a vacation without telling us, we figured out the problem.

Under Catalina and Big Sur, the check of a volume group's size returns the wrong value - it only gives the value of the system volume (which is typically 15GB or so) rather than the whole group (which is System + Data + Preboot + Recovery, etc).

Apple fixed this under Monterey, and so under Monterey and later, the warning will appear as expected.

Emulation

We found another weird problem where the system wasn't always paying attention to the "Use Rosetta" setting the user selected.

As such, under Rosetta, scheduled copies would fail in some cases, because when SuperDuper! was launched to do the copy, it wouldn't use emulation, and thus old serial numbers (see above) would fail to validate.

We now override the behavior to force emulation, on schedules, for users with old serial numbers. And, of course, if you want to run natively, and have an old, pre-2019 license, you can simply purchase a new license.

Wrapping up

That's really about it for this release. We're anticipating the release version quite soon, so speak now...and thanks to everyone who used the Beta versions and sent in feedback!

Download SuperDuper! v3.5 B5

Executive Summary

v3.5 B4 is now out, is fully Apple silicon native, and produces bootable backups for both Big Sur and Monterey. It will be offered as an automatic update for existing v3.5 Beta users, or you can download it here.

Download SuperDuper! v3.5 B4

Windier Version with Details

So far, the Beta has been going great. SuperDuper itself has been performing well, and the only real issues have, as expected, been with Apple's asr tool, which remains a black box that occasionally fails and spits out obscure errors.

Part of rolling these Betas slowly involves trying to figure out how to help users when these failures happen: basically, it's a learning process, and when we can't refer to the code, and the errors are (at best) a number and a word or two, well, it takes some time.

At this point, though, I'm relatively confident I understand how to work around most of asr's failures.

Architectural History

Years ago, when we released v3.2.5, we announced that our old e-commerce provider, eSellerate, had shut down, and they took their license recovery site with them...along with the ability to generate new serial numbers.

Despite asking quite a few times, they were unwilling to provide us with the code necessary to generate or validate eSellerate serial numbers, beyond what we already had, which was an SDK library developed for Power PC and Intel.

You'll note one significant missing chip family there.

And no, it's not 68K.

At that point, we moved to Paddle and our own licenses, which has gone well, but with the upcoming release of v3.5, we found ourselves in an interesting situation: if we wanted to release an Apple silicon-native version of SuperDuper!, we couldn't include the eSellerate license validation, since it doesn't natively support Apple silicon.

This Sounds Ominous

It'll be OK.

Here's what it means: native Apple silicon execution require new-style licenses purchased after June of 2019, when our new license system was released. Old licenses will not work natively... and if you want to run natively on an Apple silicon Mac with registered features, you'll need a new license.

What Do You Mean by "Natively"?

This does not mean you have to buy a new license! If you run with Rosetta 2 (that is, Intel emulation, set in Get Info in Finder), your existing license will work fine. All the same features are available.

But if you want the additional speed of Apple silicon (and want to future-proof yourself should Apple remove Rosetta 2 the way they removed Rosetta), or think, maybe, it's been a while since you registered, you'll want to purchase a new license.

So, Native Apple Silicon Support?

Yes!

What that all means is that this version now fully supports Apple silicon on Macs with those chips. Not much to say about that, other than we took our time and carefully tested to make sure things worked as expected, given the new chip architecture.

And they do.

Monterey Support

This version also supports Monterey, as of the current Beta release (Beta 10). It seems likely that's close to, if not the actual release version of Monterey, which I expect next week sometime, given recent announcements. They don't tell us in advance, though, so things might change.

Data-Only Encryption Support

Previous Beta versions of v3.5 didn't support encrypted data volumes, due to some tests that were required in previous OS releases. We now support pre-encrypted volumes for Data Volume Only copies (that is, copies of your stuff, with no OS, achieved with Smart Update).

Additional Improvements

We've made some changes to various bits and pieces to try to make operation under Big Sur and Monterey clearer and even more reliable.

One thing I didn't expect to be a problem is that, under Big Sur, SuperDuper doesn't explicitly say it's making the backup bootable.

This has confused people, because they think that if it didn't say it was making the backup bootable, then, well, it's not.

But it is.

Here's the deal. The asr tool, mentioned above, actually performs the bless task that makes the backup bootable. Since it was already done, we changed the wording of the "bootable" step to say it was "finalizing" the backup, since we weren't actually making it bootable any more, and I thought it was better to be accurate.

But, given the confusion, I think inaccurate-but-reassuring is a better approach.

In Sum

It's a long time coming, I know, but the final release is in sight. The feedback on the Beta versions has been almost entirely positive, and that's encouraging. So, enjoy, and let me know if you have any problems.

Download SuperDuper! v3.5 B4

On Saturday, I'll be heading up to New Boston, NH to participate in the first group ride I've done in, well, years.

I'm both looking forward to it and dreading it, because like a lot of others I'm pandemic portly, out of shape, and out of practice.

But the only way to get out of that particular rut is to start riding in some other, muddier ones...so we'll see how that goes.

More Relevant Info

What better time, then, to release SuperDuper! v3.5 B3?

This new beta is another relatively minor update that polishes the experience a bit, deals with some common situations better, and fixes a few bugs.

1. Under Big Sur and later, When you copy from a source volume group to a destination with Smart Update, we don't convert the result into a volume group with only a Data volume. This ensures the result is readily visible in Finder.

2. We've added additional information to the What's Going to Happen? section to clarify, well, what's going to happen in your particular situation (and to suggest changes if needed).

3. We've fixed a rare situation where, with certain disk configurations, the copy would fail before getting started with a "Can't obtain volume capacity" exception.

4. An old error about metadata copying failures actually said it was copying "HFS+ metadata", but it could also be APFS metadata, so now it's just...metadata. Yes, we regressed this one carefully, to ensure it didn't start saying "exFAT" or "5.25-inch floppy disk", not to mention "disk pack".

Sleepytime

One thing we've definitely noticed is that Apple silicon systems tend to sleep even when many individual processes are saying, quite explicitly, that they should not.

For example, on a scheduled copy, our schedule driver, interface and copy process all hold assertions that are supposed to prevent sleep. asr, when used, holds one itself. And yet, for some reason...

So, if you're seeing "Resource busy" errors after about, say, 10 minutes of copying, and you weren't actively using the system at the time, try setting the screen so that it "never" sleeps...

C'est Tout

So, see? Not much to say, because the beta has been working well, other than to ask you to

Download v3.5 B3

Have at it, and thanks, as always!

You know it's been a while since you last released a Beta when you don't quite remember the rhythms of the process.

But, it doesn't take long for muscle memory to kick in... and I'm happy to say that it's going really well. A lot of that is due to you: thanks for your support, encouragement and reports of both success and, occasionally, failure.

To deal with the latter (and celebrate the former), here's v3.5 B2.

A few things to mention as we continue this process:

• Make sure you have "Check for Updates" turned on in our Preferences. You may have turned it off if you were using the v3.2.5 workaround: it's time to turn it on again, since that's how you'll get Beta updates.
• Some users were confused by the macOS 11.4 Beta requirements. 11.4 is only required for M1 Macs. Intel Macs work fine with SuperDuper under all versions of Big Sur.
• Startup volumes will often not show up in the Startup Disk Preference Pane in System Preferences under Big Sur. This does not mean the drive isn't bootable—it's a weird bug in Big Sur.

  To start up from the backup, use Option+Power On on an Intel Mac, or hold down the Power button when powering on with an M1 Mac.

  If you do this, you'll note that the Mac's regular drive doesn't appear in the startup disk preference pane...but the backup drive does! It's weird. But the backup is OK! You can breathe!

• If you only made a Smart Update, and didn't start with an Erase, then copy backup, you'll note that your backup drive seems "empty". That's because you're looking at the "empty" System volume...and the Data volume is mounted by the OS as "no browse"—basically, it doesn't show up readily in Finder.

  It's still there, though. Use Finder's Go To Folder, in the Go Menu, to open /Volumes and you'll see your Data volume.

  For less stress—and who doesn't want less stress?—start with an Erase, then copy backup.

• We've actually figured out how to get at least a little useful information out of the weird errors system tools produce:

  EILSEQ -> "Illegal Byte Sequence"
  
  That, generally, means "APFS Container Corruption".
  
  Easy as pie. All errors should be decimal numbers that need to be converted to hex and byte stripped, then looked up in a file, to be useful.

  — Dave Nanian (@dnanian) May 3, 2021

For Beta 2 we've addressed a few things and polished some others: it's a relatively minor update. Details are in the Revision History, but to highlight a few things:

• Backup on Connect no longer runs over and over if you use Erase, then copy on Big Sur. This had to do with some very low-level changes to some Big Sur APIs that messed with our code that detected whether we were already running a copy for that volume.

  The bug was useful for testing a zillion back-to-back Erase, then copies, though, so there's that. Yeah! We meant to do that! Sure!

• Erase, then copy was using asr to copy Catalina, which was unintentional. It now does the same thing v3.3.1 did.
• Send to Shirt Pocket was failing for users in all versions of SuperDuper due to an locally cached response of a value that had been updated on our server. This turned out to be rather interesting, and frustrating, because we don't have a way of "fixing" old copies...although they will "fix themselves" over time...anyway, it won't happen any more in v3.5 B2 and later.

That'll about do it. Enjoy the new version, and thanks for the emails and tweets!

Download SuperDuper! v3.5 B2

Thanks, again, for using SuperDuper...we look forward to your comments.

Sound the trumpets!

We're happy (and, frankly, relieved) to announce the immediate availability of SuperDuper v3.5 Beta 1: our first version to fully support Big Sur backups.

That's right: bootable Big Sur backups for Intel and M1. Today!

Shut Up and Give Me My Download

For those who aren't interested in reading about this stuff (you really should), you can download SuperDuper v3.5 B1 from here.

Note If you're on an M1 Mac, you will not be able to boot from a SuperDuper backup unless you are running macOS 11.4 or later. The new macOS version is in beta, and you can get it here: macOS 11.4 Public Beta. (The usual caveats about running a beta OS apply.)

As you might expect, you can't boot an M1 Mac from an Intel Backup or vice versa. You can still restore, though, using Apple's "first boot" restore process, or by using Migration Assistant.

When starting off with the v3.5 beta, you must first make an erase-then-copy backup. On success, you can switch to Smart Update.

Finally, we know Big Sur Erase, then copy image backups don't work yet—Smart Updates work fine—but we wanted to get this out to those of you who have been patiently waiting. Remember: Beta!

As is always the case with our Betas, this version will automatically update to future Beta versions of v3.5 (assuming our update check is on in Preferences) until the final v3.5 is released. At that point, it will install the release version and move to the regular update check.

Let's Hear What He Has to Say!

(Have those folks in a rush gone? OK, good. For the rest of you, here's the deal.)

As we've been saying for some time, release of our Big Sur version had been gated on factors not fully in our control.

For security reasons, Big Sur forced the use of Apple Software Restore, or asr, for backups that contain a System volume (that is, any startup volume).

Until recently, asr didn't work properly with M1 Macs. It would copy the System volume, then throw various errors, including one indicating that the "source volume format was not yet supported".

Of course, the "source volume format" was APFS, something it clearly did support, so this was weird. Clearly they meant something else, like the various new support volumes the M1 Macs use.

But given that asr wouldn't run at all, there wasn't much point trying to copy the System volume. So we decided to wait, thinking that a fix would be just around the corner.

Which, needless to say, it wasn't. Or it was, but given that blocks are longer in San Francisco than they are around here (and, frankly, Apple had its hands full with a bunch of new Macs, iPads and the like), the fix took much longer than expected. So we needed to do something.

Since copying the Data volume was the only thing that worked, and was still fully restorable, we released a workaround while we waited.

This had two major advantages. First, we didn't need to fully test and beta a new version that half worked, sometimes, with caveats...something we were loath to do. Instead, it made it clear it was a workaround.

Second, it meant that we didn't have to "half wrap-up" our in-progress work.

New Stuff Has Come to Light

Of course, we kept plugging away at it and, when we checked the new macOS 11.4 beta, we were happy to see the "not yet" message had gone away, which suggested "not yet" had finally become "can". Or, at least, "might".

More testing and configuring ensued and, as of late Saturday night (livin' the high life here at Shirt Pocket HQ), we were finally able to boot from a SuperDuper copy of an M1 MacBook Pro, made to a regular USB SSD, without any post-copy OS install.

Hard to believe, but I have just booted from a backup of an M1 Mac.

Finally. Long damn road. Almost there.

— Dave Nanian (@dnanian) April 25, 2021

Finally.

As such, we can finally release a Beta that works as expected on both Intel Macs (now) and M1 Macs (assuming you have installed 11.4 Beta 1 or later).

To be clear, this is only possible because Apple made it possible in macOS 11.4. I'm certain it required changes to the M1's startup process and to asr to finally make it happen. Without those changes, we couldn't have done this in a supported way.

I'm really happy the teams involved made the effort. Thanks, folks!

The "Did I Say No Caveats?" Caveats

Remember, though, Apple is not finished. There's movement, and success, but we honestly don't know whether the final, non-beta release of 11.4 will work.

Given things are clearly changing, and heading in the right direction, we thought putting this out now would be useful.

As indicated above, you can't boot an Intel Mac from an M1 backup or vice-versa. You can, however, boot an M1 Mac from a backup of a different M1 Mac, once you've authorized it with a user on the Mac you're booting.

Regardless of processor, you can still restore using Apple's "first boot" restore process, or by using Migration Assistant. So it's not a problem to move from Intel to M1 or M1 to Intel.

Important Note asr copies at a low level and works a drive quite hard. In our internal testing, some SSDs couldn't handle the load without intermittently overheating and generating errors.

This seems to be because the controller was trying to manage freed blocks, or wear-level, while still trying to manage the flow of incoming writes.

When this happened, we started to get obscure errors from asr ("resource busy" is quite common). Allowing the device to settle and cool typically resolved the problem. I'm hoping Apple will improve its handling of this error as development continues.

We had the most success with the Angelbird SSD2GO PKT MK2, with its SSD Manager installed and the most recent Western Digital MyPassport SSD (affiliate link).

Erasing a drive from the top/hardware, rather than just erasing the volume, seems to help some drives, too.

Or you can just use Smart Update, which will only copy the Data volume. To wit...

Notes on a Revolution

With macOS releases prior to Big Sur, we could update the OS when changed, regardless of whether it was hosted on a separate System volume (as done under 10.15 and later) or on the same volume (all previous versions).

However, with Big Sur, a system update requires us to use asr to recopy the drive. And asr won't (currently?) just copy the System volume: it's all or nothing.

That's fine with an Erase, then copy backup, because you are asking for a full backup.

But with a Smart Update, fully erasing the drive when an OS changes just isn't appropriate.

So, we decided that under macOS 11 and later, a Smart Update of a "volume group"—that is, a startup volume—will only copy the Data volume, updating your applications and data but leaving the system as-is.

This gives you some interesting options:

• You can keep your backup under an earlier version of the OS, while keeping your own files and applications up to date
• It's now possible to restore just your applications and data into an existing OS install, whether through migration or by copying with SuperDuper
• By updating your backup with Smart Update, and then restoring with Erase, then copy, you can roll back the OS to the version on the backup, while keeping your most recent files and applications intact

You can think of it as a modern Sandbox: you can try a new minor OS version and still roll back if you don't like it...without losing your "new" data. Pretty nice!

Have at it

So there you go. It's been a long, frustrating road, we know—believe me, we know—but we can clearly see our destination. Enjoy the new version, thank you for your patience, and we look forward to your comments and feedback.

Download SuperDuper! v3.5 B1

Hey, folks. Sorry it's been a while, but it's been a busy time. Let's start with the bad news first.

Bad news

As you know, SuperDuper 3.3.1 cannot copy a volume with Big Sur on it. We're currently blocked on some issues I don't have direct control over, and as such I don't have a new version for you that fully supports Big Sur, nor a timeframe for when that will be released.

Right now, as many of you know, v3.3.1 will work with non-boot volumes, but it won't work with volumes that have macOS on them, because it will try to do some of the things that no longer work in macOS 11.

I know that's been a disappointment, but that's where we are with v3.3.1.

Good news!

However, after wracking my brain for far too long, I've come up with a workaround that will let you make the backups you need to save your files, and to supplement your Time Machine backup. And for that, we need to go Back...to the Future!

Huh?

Let me try to explain.

In Catalina, as I explain in Breaking the Tape, Apple split the startup volume into two parts: the System volume and the Data volume. We did a ton of work that year to support this new setup in a way that was transparent to the user; SuperDuper automatically creates the proper volumes, converts the drives to APFS as needed, etc.

Worked great.

In macOS 10.15.5, though, Apple broke 3rd party copy tools in a way that couldn't be worked around without the use of asr, a low-level drive copy tool that has its own issues. They fixed that in 10.15.6...but it was a rather ominous sign for the future.

That ominous sign became terrifying reality in macOS 11. Due to the new Sealed System Volume, use of asr became mandatory if you wanted to make a copy that was bootable. And even that didn't work at all until November 5th of last year—just before Big Sur's official release.

Even now, as of the time of this writing, asr won't make a bootable copy of an M1-based Mac.

So, as of Big Sur, 3rd party tools like SuperDuper can no longer make bootable copies on their own. For that, it's asr or nothing.

It is, indeed, a very sweet solution.

But, 3.3.1 doesn't know that. It tries to do all the special stuff that we had to do for Catalina, and those things no longer work. And so, as you've seen, that copy generates errors or seems to hang right at the start (because it's thrown exceptions that stop the copy).

Didn't You Say "Good News"?

I'm getting there.

SuperDuper! 3.3.1's magic was all about dealing with the split startup volume. It built on the APFS support and scheduling fixes we put into the previous version...and added new things for compatibility with Catalina.

But...what if it didn't do that? What if SuperDuper was...stupider?

Wonderfully Awful

I've been testing this out for a while in-house. and I've come up with a weird-sounding workaround that...works!

Basically, you can use SuperDuper to copy the Data volume of the volume group. The result contains all your data and applications, can be restored in a few different ways...and can even be made bootable.

Note that, as I indicated above, M1 Macs can't readily boot from external drives. There are things you can do, if you have an external Thunderbolt 3 drive (USB-C isn't sufficient), but even that won't work if the internal drive is dead. Unless things change, bootable backups are basically a thing of the past on M1-based Macs.

How?

It's actually easy. To accomplish this, use an old version of SuperDuper—specifically, v3.2.5—to copy the Data volume, which is shown in the older version!

v3.2.5 is well tested, having been on the market for quite some time, and is reliable. So we don't have to worry about doing a broad beta test of a partially complete new release. It's already tested, and I've been busy doing the additional testing necessary to prove it works on Big Sur.

Again, this will make a copy of the data that you need to preserve your stuff, both Applications and Data, while leaving the Sealed System Volume alone.

And it's a valid source for "restore" during a clean install or migration! So restoration is easy and fast should it become necessary.

Neat!

Yeah, I wish I had thought of this earlier.

So, if you're on Big Sur, and you want to copy a startup drive, here's what to do:

1. Make sure you have your license information handy. You can retrieve it from SuperDuper's Register... page should you need to.
2. Download and install SuperDuper! v3.2.5 from here.
3. Remove SuperDuper! from the "Full Disk Access" list in the Security & Privacy preference pane and restart your Mac. This is important, and works around an Apple bug triggered by the change of SuperDuper!'s bundle ID.
4. Run SuperDuper and follow the steps to allow it Full Disk Access.
5. If your license is missing, re-enter it from your license email.
6. Turn off "Check for Updates" in our Preferences so we don't nag you about v3.3.1.
7. Select the "Data" volume in the source pop-up, and a new APFS backup volume in the destination pop-up, along with "Backup - all files" (or whatever script you want). If you already have a backup volume, you can use Disk Utility to select and delete just the backup System volume, rather than create a new one. After doing this, rename the Data volume to something sensible (remove "- Data"). Note that you may need to repair it with Disk First Aid before it will show up in SuperDuper.
8. Make your copy as normal, set up your schedule as needed, etc. Your regular Smart Updates will work as expected.

To fully restore, it's easiest to boot to recovery, erase the internal drive you want to restore to, reinstall the OS from Recovery mode, and then, when prompted to restore during the first boot of the fresh copy of macOS, point at the backup. All your data and applications will be brought in automatically.

If you want to make the backup bootable and have an Intel Mac, boot to Recovery (Cmd+R during power on) and install Big Sur to the backup drive. You can then start up from the backup. Note, though, that once made bootable, you can no longer copy to the backup until you delete the system volume as above. So don't do this unless you need to.

Forward-Looking Statements

It seems clear that the future of bootable backups is unclear.

M1 Macs can't be copied in a way that makes them bootable. Bare metal recovery on an M1 Mac isn't possible, since they depend on the contents of their internal drive even when booting externally. And the tools required to make bootable copies of Intel Macs are limited, often fail, and produce inscrutable and undocumented diagnostics when they do.

Everything's a tradeoff, and with the M1 Macs, Apple has given us an amazing new platform, while taking away some of the things that made macOS such a joy to work with. And one of those things is bootable backups.

I have no idea if this is going to change for the better in whatever the next macOS version brings, and have no insight into Apple's future plans.

But I continue to advise multiple backup strategies, including Time Machine (to an APFS volume under Big Sur), SuperDuper! (for a simple copy of your data and applications) and an online backup program (as a last resort).

With that, back to plugging away at a new version.

Thanks for reading, and for using SuperDuper.

I'm going to keep this short and to the point.

It's never a good idea to update to a just-released major OS version unless you have to. Nobody knows how reliable Big Sur is going to be for regular users. Let someone else find out before you take the jump.

On our end, SuperDuper! will not be compatible with Big Sur on day of release.

As I indicated on twitter, the first time we were able to make a successful bootable copy of Big Sur at all was November 5th. As of this writing, that was six days ago.

Until that point, it wasn't possible.

So, it's going to be a while. Until then, if you must move to Big Sur, use Time Machine.

I haven't said anything about Big Sur yet, and since the public beta has been out for a while, and I'm getting more questions about it, it's time.

At present, it's not possible to make bootable copies of Big Sur, even with asr, Apple's own built-in replication utility. As such, we haven't released a Beta, or even an internal Alpha, because it wouldn't meet our own requirements.

So, for the moment, we're holding back, hoping that Apple will fix the issues and allow 3rd party (or even 1st party, given asr) bootable backups. While asr was failing completely in previous builds, in the most recent one it isn't able to back up because the system volume isn't properly 'sealed' (which is ominous, since why wouldn't a standard install be sealed, and if it's not, why wouldn't you be able to back it up anyway).

So, while progress is being made, we're kind of stuck waiting for the king.

In the meantime, my advice for macOS Betas remains as valid as ever: do not install a macOS Beta unless you have a critical business need to do so. These Betas, even when public, are not for general use, and certainly not for anyone who wants a reliable system for day-to-day work.

If you must install it, use Time Machine for backups for now (and, given my advice in Practices Make Perfect (Backups), on a continuing basis in addition to other methods), since it's at a relatively equivalent Beta quality level to the OS itself and is explicitly tested and supported by Apple.

I'll be back when we have additional news to share. For those in the US, enjoy Labor Day weekend!

I've probably mentioned on the blog before that I'm a big fan of electric cars.

Starting in 2013 with a first generation Tesla Model S P85, both Z and I have been powered by electrons, with two leased BMW i3s and we've now replaced the Tesla with a Porsche Taycan.

I was a guest on the I Like Batteries podcast, and like a little yapping dog who just won't shut up, I overstayed my welcome, so it was split into two parts. Part one went live today, and part two drops next week.

Enjoy! (That should probably end in a question mark, or be surrounded by scare quotes.)

https://pod.co/ilikebatteries/030-dave-nanian-likes-battery-powered-cars-part-1-of-2

Happy to say that Apple has fixed the bug in 10.15.5 that caused firmlinks to not be connected after being copied by backup programs.

As you may know, this had two symptoms:

1. The backup looked incomplete, with some folders seemingly empty on the backup drive.

   Note that the backup was complete, but because the firmlinks weren't fully connected, you couldn't see the files on the Data Volume without specifically looking for them in /Volumes (which you could access via Go To Folder in Finder).

2. The backup would boot about 2/3 of the way, and then shut down.

Both of these symptoms were caused by the same symptom. We provided a workaround on request for users who needed it, and while convenience was impacted, your data was never in danger.

Fortunately, it's fixed in 10.15.6, and a normal Smart Update will repair your backups and all will be back to normal.

Until Big Sur, of course...where the "adventure" continues. More on that when I have something good to say.