Description:

RFC 5716 introduces the Federated File System (FedFS, for short). FedFS
is an extensible standardized mechanism by which system administrators
construct a coherent file name space across multiple file servers using
file system referrals.

A file system referral is like a symbolic link to another file system
share, but it is not visible to applications. It behaves like an
auto-mounted directory where a new file system mount is done when an
application first accesses that directory. The arguments of the mount
operation are controlled by information returned by the file server.

Today, file system referral mechanisms exist in several network file
system protocols. FedFS provides its file name space features by
leveraging referral mechanisms already built in to network file system
protocols. Thus no change to file system protocols or clients is
required.

Currently, the Linux FedFS implementation supports only NFS version 4
referrals. More on NFS version 4 referrals can be found in RFC 3530.
FedFS may support other network file system protocols in the future.