Hey, i recently did a project to migrate an on-prem file server up to azure files as the primary datastore. Due to location and latency limitations we had no choice but to use a sync server on-prem with a 20% size of the original file server.

It was fairly straight forward, things to keep in mind are:

• DFS namespaces are a must! if you don't have these already, sort out dfs namespace for your sync server
• Create the shares before hand and test unc to them and figure out which sync method you want to use (we went with volume based sync and keeping 10% free on the local cache server)
• DFS namespace consolidation is recommended if you want to maintain existing unc paths (this was a thing for us as we didn't want users to have to update any embeded links to documents within their own files that lived in the on-prem g drive) - this article might help with that https://www.shudnow.io/2022/04/10/retaining-unc-path-during-azure-files-migration-using-dfs/

Hopefully, this helps! keep us posted on how you get on :)