InterMezzo

InterMezzo was a distributed file system written for the Linux kernel, distributed under the GNU General Public License. It was included in the standard Linux kernel from version 2.4.15 but was dropped from version 2.6. InterMezzo is designed to work on top of an existing journaling file system such as ext3, JFS, ReiserFS or XFS. It was developed around 1999. An InterMezzo system consists of a server, which holds the master copy of the file system, and one or more clients with a cache of the file system. It works either in a replication mode, in which a client maintains a duplicate of the entire file system, or in an on-demand mode in which the client only requests files that it needs. It does this by capturing all writes to the server's file system journal and streaming them to the client systems to be replayed. InterMezzo is described as a "high availability file system" since a client can continue to operate even if the connection to the server is lost. During a period of disconnection, updates are logged and will be propagated when the connection is restored. Conflicts are detected and handled according to a "conflict resolution policy" (although the best policy is likely to be to avoid conflicts). Typical applications of replication mode are: A cluster of servers operating on a shared file system. Computers that are not always connected to the network, such as laptops.