Over SMB.
> Since these are backups, shouldn't they be read only? A snapshot at least would ensure easy rollback.
My digital archive is not a backup. It is digital storage which I actively use every day, and which is itself backed up. Windows is not deleting the file from the backups, but I don't keep old backups forever.
That would make sure the important files are still available (even over smb) by going to the hidden .zfs directory inside the zfs file system.
I'd probably do something like create a new ZFS file system on your server just for these special files, move them into it, snapshot the file system to ensure they're preserved, then make the filesystem available over the network via a new SMB share.
That's just a rough first idea. If you're changing those special files much, then some kind of automatic timed snapshot thing (maybe with expiry) would probably be useful too. aka cronjob