This options is a noop on s3 but on the posix implementation it becomes useful
when there isn't the need to have a persistent file, thus avoiding some fsync
calls.
* Rename to datamanager since it handles a complete "database" backed by an
objectstorage and etcd
* Don't write every single entry as a single file but group them in a single
file. In future improve this to split the data in multiple files of a max size.
Simone Gotti