B2 bucket size smaller than Kopia snapshot?

Disclaimer: I’m completely new to the backup game, not comfortable with the CLI, using KopiaUI only.

I just completed my first snapshot backup of my external drive to my B2 bucket. In KopiaUI, I see that my volume size is 186.5 GB (which correctly matches the total size of the external drive files I’m snapshotting, when I inspect them in Finder).

However, my B2 bucket size is only 170.5 GB. (I tried snapshotting again and refreshing B2 to double-check.)

Is this possibly due to Kopia’s encryption method containing some kind of compression? Or have I lost data in my B2 bucket?

There are two possible reasons:

  1. compression - which I think is none by default - see in policies.
  2. deduplication - the same data is stored only once

To be safe run full restore and check - it is good exercise anyway to test if all works.

Thank you for your reply! I didn’t think about deduping - that makes sense since most of my files are photos and it’s not unlikely that I have the same photo in different folders. I just checked my policies and my compression is indeed set at none.