|Initial release||4 January 2005|
|Stable release||3 (25 July 2012)|
|Operating system||Mac OS X|
|Type||Shared disk file system|
Xsan is Apple Inc.'s storage area network (SAN) or clustered file system for Mac OS X. Xsan enables multiple Mac desktop and Xserve systems to access shared block storage over a Fibre Channel network. With the Xsan file system installed, these computers can read and write to the same storage volume at the same time. Xsan is a complete SAN solution that includes the metadata controller software, the file system client software, and integrated setup, management and monitoring tools.
Xsan has all the normal features to be expected in an enterprise shared disk file system, including support for large files and file systems, multiple mounted file systems, meta data controller failover for fault tolerance, support for multiple operating systems, etc.
Xsan is based on the StorNext File System. The StorNext File System and the Xsan file system share the same file system layout and the same protocol when talking to the meta data server. They also seem to share a common code base or very close development based on the new features developed for both file systems.
The Xsan website claims complete interoperability with the Quantum Corporation StorNext File System: "And because Xsan is completely interoperable with Quantum’s StorNext File System, you can even provide clients on Windows, Linux, and other UNIX platforms with direct Fibre Channel block-level access to the data in your Xsan-managed storage pool."
Quantum Corporation claims "Complete interoperability with Apple’s Xsan and Promise RAID and Allows Xsan and Xserve RAID to support AIX, HP-UX, IRIX, Red Hat Linux, SuSE Linux, Mac OS X, Solaris, and Windows clients, including support for 64 Bit Windows and Windows Vista."
All the command line tools for Xsan begin with the letters cv, which stand for CentraVision – the original name for the file system.
Data representation 
Xsan file system uses several logical storages to distribute information. The two main classes of information appear on Xsan: the user data (such as files) and the file system metadata (such as folders, file names, file allocaton information and so on). Most configurations use different storages for data and metadata. The file system supports dynamic expansion and distribution of both data and metadata areas.
On 4 January 2005, Apple announced shipping of Xsan.
In May 2006, Apple released Xsan 1.2 with support for volume sizes of nearly 2 petabytes.
On 5 December 2006, Apple released Xsan 1.4.1.
On 18 October 2007, Apple released Xsan 1.4.2, which resolves several reliability and compatibility issues.
On 19 February 2008, Apple released Xsan 2, the first major update, which introduces MultiSAN, and completely redesigned administration tools. 2.1 was introduced on 10 June 2008. 2.1.1 was introduced on 15 October 2008. 2.2 was released 14 September 2009.
On 25 August 2011, Apple released Xsan 2.2.2, which brought along several reliability fixes.
On 25 July 2012, Apple released Xsan 3, included Xsan in OS X Mountain Lion 
- "Apple Introduces Xsan Storage Area Network File System".
- "Xsan Introduction".[dead link]
- "Apple Introduces Xsan Storage Area Network File System". Apple Inc.
- "Xsan 2 for traditional IT services".
- "StorNext FX and FX2".
- "Apple Ships Xsan Storage Area Network File System". Apple Inc.
- Info-Mac: View Topic – Apple Introduces Xsan 2[dead link]
- Apple Releases Xsan 2.2 Updates
- Apple Releases Xsan 2.2.2 Filesystem Update