Some sites may want to use a wrapper script for unoconv to force it to always perform processing on a node that is not a webserving node. This would be fairly simple - except that we use a request only dir for file conversions which would need to be mounted on both servers.

Instead we should use make_temp_directory and clean up after ourselves. This will have no performance impact on single node servers, and is desirable for clustered sites.

This is all in lib/filestorage/file_storage.php