Distributed filesystems are those where the files are distributed in whole or in part on different block devices, with direct interaction with client computers to allow IO scaling proportional to the number of servers. Acording to this definition, a network-shared NFS server would not be a distributed filesystem, whereas Lustre, Gluster, Ceph, PVFS2 (aka Orange), and Fraunhofer are distributed filesystems, altho they differ considerably on implementation details. While NFS is a well-debugged protocol and has been designed to cache files aggressively for both reads and writes, the single point bottleneck for IO, is a real weakness in a compute cluster environment.
Mangalam concludes that FhGFS is a very capable technology and one that is worth examining in more detail if you need a cheap, very fast, distributed-only filesystem. He has also found Gluster to be remarkably stable. Read the Full Story.