===== Clustered File Systems

GFS: Global File System.
    GFS, available in Linux, is the most widely used clustered file system.
Developed by Red Hat, GFS allows concurrent access by all participating cluster
nodes. Metadata is generally stored on a partition of the shared (or replicated)
storage.
OCFS: Oracle's Oracle Clustered File System.
    OCFS is conceptually very much like GFS, and OCFS2 is now available in
Linux.

VMFS: VMware's Virtual Machine File System.
    VMFS is the clustered file system that ESX Server uses to allow multiple
servers access to the same shared storage. This makes virtual machine migration
(to different servers) seamless, as the same storage is accessible at the source
and destination. Journals are distributed, and there is no single point of
failure between the ESX servers.

Lustre: Sun's clustered, distributed file system.
    Lustre is a distributed file system designed to work with very large
clusters containing thousands of nodes. Lustre is available for Linux, but its
applications outside the high performance computing circle are limited.

Hadoop: a distributed file system, like Google uses.
    This is not a clustered file system, but rather a distributed one. We
include Hadoop because of its rising popularity, and the wide array of storage
architecture design decisions that can take advantage of Hadoop. By default, you
will have three copies of your data on three different nodes. Changes are
replicated to each, so in a sense it can be treated as a clustered file system.
Hadoop does, however, have a single point of failure: the name node, which keeps
track of all file system level data.