Time Machine backup of an external drive (to another external drive)

Question

I back up my internal drive to an external backup drive using Time Machine. I would also like to back up a 1TB external drive of mine, to another 1TB external drive of mine.

Is it possible to make Time Machine-styled backups of my external drive to the other external drive?

By Time Machine-style backups, I mean the way that Time Machine makes easy-to-browse "snapshots" on the backup drive, where you can view the source drive at different times by accessing different folders on the backup drive.

I considered two ways to achieve this:

1. rsync using the --backup option

   • This moves all deleted files into a separate backup directory wherein it preserves the original file structure. Good, but not exactly the Time Machine styled backups I'm looking for.
   • This also (to my knowledge) won't work for finding old versions of editing files.

2. Carbon Copy Cleaner

   • This has the disadvantage again—all the deleted (and I believe modified files) are moved to a "safety net" directory.

However, neither of them achieve the "browse different snapshots" behavior, à la Time Machine that I'm looking for.

Is there any way to achieve what I'm requesting?

I realize that it's possible with Time Machine itself, but from what I understand, it will only back the external disk up to my main backup disk. I want the external disk to backup to a secondary backup disk, keeping these backups separate from each other, mainly due to space limitations.

Answer 1

I have finally found the perfect answer to this. Behold the aptly-named rsync-time-backup project on GitHub. This is an easy-to-use bash script which can back up a source folder to a destination folder. Each backup made will create a time-labeled folder in the destination directory containing a full mirror of the source folder at that time, à la Time Machine.