Hi, Charles.
S3 doesn’t work like a “drive” – it’s a key-value storage bucket somewhere else. EFS is a drive but not S3. There are tools that will claim to bridge that gap and present S3 like a drive, but I’ve never been impressed with their performance or stability.
You do have some options, though.
One, consider narrowing the scope of the shared partition. While trying to serve OpenEMR from S3 will never be performant, one of these “drives” that just served the patient documents (and not OpenEMR’s templates)… I dunno, might work? Any solution that puts something like sqlconf.php anywhere other than the local machine is just a catastrophe waiting to happen.
Two, if document storage is your primary concern, consider spinning up a CouchDB instance and using that for document storage.
Three, consider Amazon EFS, which is a networked file share that’ll do what you’re wanting to see done here.