PFS (Personal File System) is a portable network file sharing system
designed for mobile computers. It is constructed from file servers
on stationary hosts and mobile clients. It has a cache storage on
the client, and dynamically adapts for variety of network speeds
and bandwidths includes disconnection. All of PFS system is
implemented on user land on UNIX, and communicates with client
kernel with traditional NFS. Then, PFS can run on variety of UNIX
variants.

In short, you can mount file server's disks onto your laptop computer
over the network, and you can continue accessing to these files
even when your computer disconnected from the network. You have no
need to modify Operating Systems on both server and client!

http://www.spa.is.uec.ac.jp/%7Etate/pfs/
