Is there a detailed explanation of the storage format and directories? It does not seem logical that if I were to replicate the exact storage from one target to another, that it would possibly not work. (I was surprised when I read to only copy the "chunks"folder in any case.)
To simplify it with an example: If I make two SMB mounts identical by copying all the files and directories from one to the other…including file properties, how can it be that only the original mount will be assured to work, but the copy is not assured to work??? They are identical.
Also: It seems like a relatively common scenario where backups would go to an on-site location and then be “replicated” to cloud storage. There is a kludgy way to do this by making a “dummy repository”. If the COPY command is the only reliable way to make two stores identical (yes, you can copy only subsets of revisions), can I suggest a FR to make a “SYNC” command that just simplifies that configuration? Then maybe there’s an easy “ADD -MIRROR” you could run on your local repositories?
To the original question, there are a lot of “moving parts” in these configurations. Standardizing on terminology would be a huge gain in users comprehending how to configure and how it works. (And I agree with @mathome1 that “snapshot_id” is an awful synonym for “repository_id”, as traditional backup terminology uses “snapshot” generally where you are using “revision”.)
Documenting that “during a copy, repository_id is not used, because it is copied along with the source’s info” would be very helpful if that’s the case. When the -COPY option is specified, it would be even better to NOT require the parameter at all.