How can I validate dedup behavior


I’ve setup a kopia server behind an Apache proxy and created 2 user accounts (1 for each client).
Both clients are macOS 14 computers.
I would like to check that an existing file on both side is properly deduped, hence uploaded only once by the 1st client creating a snapshot on the server.
How would one does that?

Have you tried checking the repository size? If the file size is large enough, it would make a visible bump. Like for example, a 1 GB duplicate file on 5 GB backup + 10 GB backup would result in a total of around 14 GB instead of 15 GB with deduplication (assuming no compression).

I’m looking for an analytic method, for example a command to list the number of occurrences for a given file in a repository. I’m not looking for an experimental method that would not allow me to inspect previous uploads.

Related question: if client A upload file Foo on a repository & client B uploads the same file Foo to the same repository, does the dedup process assign the same Object ID to both files or does each «upload» of the same file lives its life with a different Object ID?