Editing InterMezzo (file system)

{{Infobox software
| name                   = InterMezzo
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| developer              = [[Peter Braam]]
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| genre                  = [[distributed file system]]
| license                = [[GNU General Public License]]
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'''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 (operating system)|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]], [[IBM Journaled File System 2 (JFS2)|JFS]], [[ReiserFS]] or [[XFS]]. It was developed around 1999.

An InterMezzo system consists of a [[Server (computing)|server]], which holds the master copy of the file system, and one or more [[Client (computing)|clients]] with a [[Cache (computing)|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 (computing)|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 [[laptop]]s.

Typical applications of on-demand mode were distributed file serving, such as [[File Transfer Protocol]] (FTP) or [[WWW]], or desktop workstations.

InterMezzo was started as part of the [[Coda (file system)|Coda]] file system project at [[Carnegie Mellon University]] and took many design decisions from Coda (but did not share code). Coda in turn was a branch from the [[OpenAFS]] project.<ref>{{Cite news |title= Using the InterMezzo Distributed Filesystem |author=  Bill von Hagen |work= Linux Planet |date= August 12, 2002 |url= http://www.linuxplanet.com/linuxplanet/reports/4368/1/ |url-status=live |archive-url= https://web.archive.org/web/20030402131112/http://www.linuxplanet.com/linuxplanet/reports/4368/1/ |archive-date= April 2, 2003 |access-date= September 23, 2013  }}</ref>
It was designed for enhanced scalability, performance, modularity, and easy integration with existing file systems. 
A paper was presented at an Open Source Convention in August 1999 by [[Peter Braam|Peter J. Braam]], Michael Callahan, and Phil Schwan.<ref>{{Cite news |title= A report from the Open Source Convention |author= Vicki Brown |date= September 1, 1999 |url= http://www.sunworld.com/sunworldonline/swol-09-1999/swol-09-osconf.html |url-status=dead |archive-url= https://web.archive.org/web/20010204001000/http://www.sunworld.com/sunworldonline/swol-09-1999/swol-09-osconf.html |archive-date= February 4, 2001 |access-date= September 23, 2013 }}</ref>
A company called Stelias Computing created a web site in late 1999, and announced a "beta" test version in January 2000.<ref name="site">{{Cite web |title= Archive of the Inter-Mezzo.org web site |url= http://inter-mezzo.org |url-status=dead |archive-url= https://web.archive.org/web/20000520193359/http://inter-mezzo.org/index.html |archive-date= May 20, 2000 |access-date= September 23, 2013  }}</ref>

Although it was supported in the standard Linux kernel in version 2.4, InterMezzo was removed in the 2.6 series. Its developers moved on to a new project named [[Lustre (file system)|Lustre]] at a company called Cluster File Systems, around 2001. Development continued through about 2003, and the web site was maintained through 2008.<ref name="site" />

== See also ==
{{Portal|Free and open-source software}}

* [[rsync]]
* [[Coda_(file_system)|Coda]]
* [[Lustre (file system)|Lustre]]

==References==
{{Reflist}}

==External links==
* [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=78855 Debian Bug report logs on InterMezzo, mentioning Lustre].

{{DEFAULTSORT:Intermezzo (File System)}}
[[Category:Network file systems]]
[[Category:Virtualization software for Linux]]
[[Category:Distributed file systems supported by the Linux kernel]]