Simplest solution for mirroring data to an external drive?

I sometimes copy a bunch of files to my Mac’s internal drive. I also have a new external drive plugged-in. What’s the simplest way to have macOS automatically mirror/copy files from a folder on one drive to a folder on another? I’m not really looking for a formal backup strategy here. But I guess some kind of rule maybe? Thanks in advance!

Do you use a backup app? Many backup apps like Carbon Copy Cloner, Resilio Sync and ChronoSync will let you select parts of a drive you want to clone, down to the folder level (and of course on subsequent runs will only copy over changes after the first copy).

Otherwise there are folder-sync apps aplenty, like Good Sync, but the better folder-sync apps cost $30-ish, close to that of a good backup app.

If you’re cheap and are willing to get geeky, look into the rsync command built into macOS - you can even automate it with Automator.

Personally, I’d just create a file-sync process in my backup utility that copies the subset of folders I want to mirror.


You can also try a sync solution like resilio sync

Their free option gives you a lot to get this done already, and they’ve got a lot more in the premium tier. For my needs the free one was enough for many years, but I now upgraded to pro for some specific needs.

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An app like Hazel can watch a folder and act on files that arrive, but that is more about tracking activity than maintaining a mirror. As already mentioned, apps like Carbon Copy Cloner can mirror directories, and can do so on a schedule, which may suit your needs.

A wild idea that I do not endorse as such, it just occurred to me, might be to get Hazel to set off CCC or equivalent.

There is also macOS’s native Folder Actions to consider.

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Great ideas, thanks, all!

I believe that if you want to do selective sync of specific folders you need the $60 version of Resilio. CCC is $40, Chronosync is $50.

That’s selective sync only. So what NOT to sync.
I believe the question here is what TO sync. I’ve used that with the free version for years.

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