in cabinet FS copy

I thought I had read if you copy deduped data to another deduped fs you should be ok? or is that only in replication?

fs_copy is used to create complete or differential copy of a file system, where source and target file systems have to be identical size. You might want to look into server_archive command but remember if you copy data that has been deduped, it will first get "un-deduped" and then copied to the target, so in the process you will lose all deduplication.

i think it only applies to replication and fs_copy since those are block level copy.

correct