[f4: Facebook’s Warm BLOB Storage System](https://www.usenix.org/system/files/conference/osdi14/osdi14-paper-muralidhar.pdf), and has a lot of similarities with [Facebook’s Tectonic Filesystem](https://www.usenix.org/system/files/fast21-pan.pdf)
On top of the object store, optional [Filer] can support directories and POSIX attributes.
Filer is a separate linearly-scalable stateless server with customizable metadata stores,