Lustre is a NetworkFileSystem designed for very large clusters, aiming for high scalability and availability. Amazing performance is a stated goal.
It was started as a replacement for Intermezzo, which in turn was meant to be a better Coda. Version 1.0 is now available. It does not support DisconnectedOperation, but that is planned for 2.0.
Cluster File Systems, Inc. are the primary maintainers of Lustre. They also offer commercial support for it.