Time Machine, Carbon copy cloner and Backblaze are all failing to back up my data completely.

Are any of these missing files in your iCloud Drive? CCC (and Time Machine) won't copy "cloud only" items by default, so those wouldn't be present on the backup. You can set up a separate task to back up cloud-only content with CCC though.

If you haven't done so already, choose "Report a problem" from CCC's Help menu to open a support request. It can also be helpful if you can include a screenshot showing two Finder windows that compare the same folder on the source and backup volume (you can attach screenshots in the followup email you receive after submitting the request). We're happy to help get to the bottom of this.

Mike (developer of CCC)

<< all three are failing to backup all of my files. >>

how did you decide that?

Time machine backups after the first one provide an Incremental backup -- the most recent time machine backup folder will contain ONLY the changed files.

Time machine backup folders were never intended to be looked at or manipulated with FINDER. The correct way to see the backed-up files in a Folder is to navigate to the Folder to be examined, the choose 'Enter Time Machine' from the Time Machine MenuBar item.

After a moment, you will see the most recent backed-up state of that folder. Stacked behind that is the state of that folder, receding back, back, back in time. like this older version:

I've used CCC for years with no issues.

Also, what do you mean by not backing everything up? The default is to only backup data that does not belong to the OS. You won't see anything from the System folder or most of the root Library folder in the backup.

This is by design. As the developer of CCC has said, Apple's security of Big Sur and later makes it impossible to know if everything has been backed up when you're trying to clone the entire drive. They strongly suggest not doing that.

Yes, that's the issue with Carbon Copy Cloner (CCC) when used with Dropbox and other cloud backups. Those cloud backups are linked and somewhat hidden. When you navigate through your external backup drive, you'll think the files are there but they're really not. Using Dropbox backup for the "Documents" folder is risky simply because copying backups like CCC can't actually see the files - they're virtually linked.

For instance, on my one M2 Macbook air, Finder shows a little "document" icon inside of the Documents folder, and it also shows a tiny little gray lock icon. When I click onto that folder, it appears all my media is in documents. Great, right?

Nope! When I plug in the external backup drive to my iMac or another MB Air, I look at the folders. There, I see the /drive/Users/UserName/Documents folder is in fact completely empty. Nothing. And under the .Mac2xxx folder dropbox creates, if I dig around, I can find the hidden linked Dropbox folder. But again, that folder is empty.

So, in fact the files aren't backed up.

If you have the external drive connected to the computer running Dropbox backup, you'll think your files are safe. But if you plug that drive into another computer and truly try to verify the files are there, you'll be in for a surprise. Your files aren't backed up.

In CCC, there's an option under "Advanced Settings" to "Temporarily download cloud-only files to make a local backup". That may work, it may not.

The warning is - verify the files are actually on the drive by connecting it to another, separate computer so Dropbox can't fake/hide what's actually not there. When your computer crashes or you do a major OS upgrade and something goes wrong, and Dropbox gets hacked/deleted/whatever, you'll think your external drive has the files when in fact it doesn't.

Losing all her data happened to my girlfriend's computer once, so I'm much more fanatic about checking on another, separate computer with a separate account. You'll be surprised at what's actually missing.

Understood. But the question is, why?

Anything that is not part of the OS should be copied by CCC to the target drive. If the file is not on the source drive you've chosen, it will not copy. CCC does not concatenate all mounted volumes during a backup.

The backup volume will look something like this:

So if the PDF in question is (example) on your desktop, then it will be with the Users folder.

"On the cloud" is great for sharing photos, but is not a viable backup solution for everything you have. 

As you have discovered, some of the disk based backup programs (for whatever reasons) do not back up onto the disk if the file is "on the cloud" . That is not the behavior I would ask for, if given the choice.

Just to reiterate, CCC *does* give you the choice to make a local backup of cloud-only content. We recommend that you set up a separate task to back up cloud-only content, though, because that content could consume more space than the original source has capacity for – you don't want to create a backup of your startup disk that can't be easily restored back to the same startup disk.

I do not fault CarbonCopyCloner is any way for this predicament.

[in my opinion] solving the problem of 'not-quite-enough disk space at the moment' by choosing to borrow the space needed from Cloud storage is a "Deal with the Devil".

[in my opinion] for best stability and reliable backups, that 'borrowing' of cloud space should be paid back using real local disk space, and sooner rather than later. The virtual "interest" is accruing, and soon, you may not be able to easily go back toward "Best Practices" of everything under your local control and being backup up in a completely predictable and re-creatable way on local disks.

Imagine a drive failure with half you stuff "on the cloud". Getting everything back could be quite complicated at a time when you want it to be dead simple, to avoid making a mistake and losing files.

[in my opinion] you should try to resist the temptation of "free" extra space on the cloud (or take that 'loan' but pay it back quickly) -- it could be a nightmare waiting to happen. Buy more drives. They are really cheap by historical standards.