Bombich Software Blog

For many macOS users, myself included, this phrase can be triggering. Maybe you've bumped into it once or twice after errantly detaching a disk without unmounting it first -- if that's you: you'll find the short version in the what to try section below, and the rest of the article explains the "why" if you're curious.

But this one is especially for the beleaguered -- the people who have dismissed that alert not a handful of times, not even dozens of times, but seemingly hundreds. If that sounds like you, you're not alone, and we're going to get to the bottom of what's actually going on.

How does a disk actually get mounted in the first place?

When a storage device is attached to a Mac, several services collaborate to present the content of that storage to the user in the Finder. IOKit, the manager of hardware devices, is the first system service to see the device (via the "kernel_task" process). IOKit will create an...

One of the big reasons people don't back up more often? Backups take too long. On a disk that's filled with data, even a routine backup can drag on — not because much changed, but because CCC has to stop and check every file and folder just to find out. CCC's Quick Update feature cuts straight to the chase: it asks macOS which folders actually changed and skips everything else. Faster backups mean you can comfortably back up more often, which means your backups are more likely to be fresh when you need them.

How does Quick Update work?

macOS has a handy service that tracks filesystem activity on your local drives. When a backup task runs, CCC can ask this "FSEvents" service for a list of folders that contain files that have been modified since the last time the backup task ran. CCC then limits its comparison activity to only that smaller collection of folders, rather than performing an exhaustive enumeration of every file and folder on the source and destination.

Why is Quick Update so much faster?

When you're dealing with slower storage like most backup disks, it might take a...

A routine backup that should have finished in minutes was instead dragging on for hours. The culprit turned out to be a tiny menu bar clock app that had quietly sprouted a million empty folders. Here's how we tracked it down – and how one very persistent customer finally dug his way out.

The user, "John", noticed his backup task was taking much, much longer than expected. He had CCC submit logs alongside his request, so I was able to review the details of the events. Two stats in the prescan result stuck out prominently:

📊 Totals: files: 2,622,988, symlinks: 3,766, folders: 1,083,778, data: 601.9 GB. Scanned in 15353s

4 hours to enumerate the source! I checked the source device details – it was the startup disk in an Apple Silicon Mac, so definitely not slow. Other context indicated that the startup disk performance was generally just fine.

The smoking gun

The folder count was suspicious, too – about 5x higher than usual for that file count. After slogging on a while longer, CCC's stall detection flagged exactly where the task was getting stuck:

🔺 Stall encountered...

Your Mac backup drive holds years of photos, financial records, work files — an external copy of nearly everything on your Mac. But what if that backup drive slips out of your bag at the airport, gets swiped from your car, or is taken in a home burglary? Without encryption, whoever has that drive has everything on it. With FileVault encryption enabled, they have nothing but unreadable data. This is what's known as "at-rest" protection, and Carbon Copy Cloner makes it a one-click setting on any APFS backup volume.

How do I enable encryption on my CCC backup?

When you initially select a volume as a destination to a backup task, CCC's Backup Volume Setup Assistant will offer an option to enable encryption. Simply check the box to enable encryption and provide the password that you would like to use to unlock the volume. If your backups are already configured, you can do the following to enable encryption on a volume:

1. Click Volumes in CCC's sidebar.
2. Select your backup volume in the sidebar.
3. Toggle the FileVault switch to the On position.
4. Enter a password to use for unlocking the volume, then encryption conversion will begin.

Every March 31st, we celebrate World Backup Day, a day to show our love for our data and how important it is to keep it safe. To kick off that celebration, we're releasing CCC 7.1, loaded with some great improvements and a handful of new features. And since it's spring, we have a little Easter egg too and some helpful tips for spring cleaning your Mac.

What's hatching in CCC 7.1?

Thanks to some new macOS functionality, CCC no longer has to install its privileged helper tool in a special system folder. The helper tool will still be registered with macOS, but it'll stay inside the CCC app bundle. This new way of doing things fixes a bunch of issues that have come up over the years with the old LaunchDaemon setup as Apple has improved macOS platform security. That perplexing "A macOS System problem prevented CCC from installing its helper tool" dialog is a thing of the past. It also gets rid of some Full Disk Access headaches — CCC's helper tool no longer needs its own Full Disk Access permission. Sadly, that means we're saying goodbye to the CCC Privacy Fish! No...

While some developers seem surprised by a change in macOS 15.2, we've known for several years that making bootable backups would eventually become impossible. We shifted CCC's strategy away from relying on External Boot so our users wouldn't be affected by this inevitable result.

I took a few days off last week to help a family member, and returned to find the Mac community all aflutter with comments about bootable backups not working after the 15.2 update and comparisons of Apple to The Grinch. After reviewing a lot of comments on this subject, I felt it was time to weigh in. Apple is taking a lot of heat for this "bug" in 15.2, but if there is any finger-pointing here, I think it should be directed towards any developers that have misled their users into believing that ASR and "bootable backups" had any place in a backup/recovery strategy post-Big Sur.

This result does not come as a surprise

Several years ago I wrote a blog post about the macOS Big Sur changes that affected how third-party developers would be able to make copies of the System:

Beyond Bootable Backups: Adapting recovery strategies for an evolving...

I had the opportunity to evaluate the new U34 Bolt from Oyen, and I was only disappointed that this device doesn't literally scream or burn a hole through the desk. While delivering a stunning 3.1GB/s of sustained throughput, it was completely silent and no warmer than a cup of coffee (120°F/49°C). As exciting as that was, though, I thought this would be a good opportunity to explore why we don't always see peak performance from a storage device.

Please note that we never accept any type of compensation for product recommendations. The only benefit we receive from recommendations is positive experiences with our software.

Interface performance vs. device performance vs. filesystem performance vs. software performance

Perhaps once a month we'll get a comment, "Black Magic Speed Test shows XX MB/s, but the backup only gets YY MB/s. What gives?". Less frequently people will wonder how to find that 40Gb/s performance that Thunderbolt boasts. First, let's address the math that may not be obvious. "Gb/s" is not the same as "GB/s"; Gb/s is "Gigabits per second", GB/s is "Gigabytes per second". There are 8 bits in a byte, so 40Gb/s is comparable to 5GB/s. But, interface performance isn't...

There's one aspect of our company that I take a lof of pride in: our engineering team works directly with end users to solve problems and to create backup strategies. We don't have multiple tiers of support and focus groups, no chat bots or AI – we just talk directly with people. With that feedback going directly into product development, we're constantly polishing every aspect of CCC so that it works exactly the way it feels like it should. We want your backups to be successful, and we feel personally accountable for your success.

One common pattern of feedback we've gotten is that getting a backup volume formatted can be kind of challenging. What partition scheme to use, which format, how many volumes, which volume for what purpose – it can add up to a lot of decisions and steps! It's also too easy to do it in a suboptimal way, and not realize that your backup strategy is missing some key feature.

Today we're introducing CCC 7, which is loaded with new features and enhancements specifically designed to help you build a robust, flexible and successful backup strategy. At the top of the list is a backup volume setup...

We're on the eve of World Backup Day – March 31st (because you're an April Fool if you didn't back up on March 31), so now is a great time to revisit some Backup Best Practices. If you're already using CCC for your backups, you've got a great leg up! If you haven't given it a whirl yet, today is a great day to try it out.

We all want our backups to protect our data; that's the obvious reason for making them. But we also want them to be reliable, easy to use, fast, and generally out of sight. It's like that furnace in your attic – you want to know that it's working, but you don't want to have to think about it every day. Once a year, though, maybe you should give it some attention to make sure the condensate isn't going to start leaking through the ceiling. (Yes, that's a very specific analogy 😉)

Here are a few suggestions to get your backup strategy in top-shape.

Create a backup on directly-attached storage

NAS and cloud-based backups feel really convenient – until you have to restore a lot of data from them, or migrate that data...

We field a lot of support requests, and similar to a doctor's office, we see some extreme cases. One of those interesting extreme cases are folders with high file counts. Any time a folder has more than a few thousand items in it, the filesystem is going to be a lot slower when working with that folder. Adding a new file, for example, requires that the filesystem compare the new item name to the name of every other file in the folder to check for conflicts, so trivial tasks like that will take progressively longer as the file count increases. Gathering the enormous file list will also take progressively longer as the list gets larger. The performance hit is even more noticeable on rotational disks and network volumes, so we often see these sticking out in backup tasks.

Sometimes high folder counts can bring a backup task to a halt

Last week, one of our users found the task as shown above. Upon closer analysis, we determined that the "media" folder had 181,274 files in it. In other words, more than 10% of the files on the...