This tutorial shows how to combine four single storage servers (running Debian Lenny) to one large storage server (distributed storage) with GlusterFS. The client system (Debian Lenny as well) will be able to access the storage as if it was a local filesystem. GlusterFS is a clustered file-system capable of scaling to several peta-bytes. It aggregates various storage bricks over Infiniband RDMA or TCP/IP interconnect into one large parallel network file system. Storage bricks can be made of any commodity hardware such as x86-64 servers with SATA-II RAID and Infiniband HBA.

http://www.howtoforge.com/distributed-storage-across-four-storage-nodes-with-glusterfs-on-debian-lenny