The Veritas File System, (or VxFS, called JFS and OJFS in HP-UX ), is an extent-based file system. It was originally developed by Veritas Software[1] which merged with Symantec in 2005. Through an OEM agreement, VxFS is used as the primary filesystem of the HP-UX operating system, although HP-UX calls it JFS. A variant with on-line defragmentation and resize support is known as OJFS.[2] It is also supported on AIX, Linux, Solaris, SINIX/Reliant UNIX and UnixWare. VxFS was originally developed for AT&T's Unix System Laboratories. VxFS is packaged as a part of the Veritas Storage Foundation (which also includes Veritas Volume Manager).
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History
According to the vendor, it was the first commercial journaling file system.[3] That claim can be taken in two ways, e.g., the first implementation of a journaling file system in a commercial context, or the first file system available as an unbundled product. Dan Koren is cited as one of the original developers of VxFS.[4] He notes in a mailing list that they "finished release 1.0 one year or so later" after starting development of VxFS under a contract with AT&T in 1990.[5] Other sources agree that the product was first released in 1991.[6][7]
Layout versions
The on-disk layout of VxFS is versioned and upgradeable while the file system is mounted. The version 5 on-disk layout of VxFS supports file systems up to 32 terabytes in size. Individual files can be up to 2 terabytes in size. Version 5 was introduced in VxFS 3.5. The version 6 on-disk layout supports file systems and files up to 8 exabytes in size. Version 6 also introduced support for named streams/resource forks, for multiple underlying volumes, and for file change logs. Version 6 was introduced in VxFS 4.0. The version 7 layout introduced in version 5.0 extends support for multiple volumes to permit Dynamic Storage Tiering. Dynamic Storage Tiering allows root users to move files among different volumes, allocate files to different volumes at file creation time based on policy, and independently recover volumes, without altering the namespace of the file system.
Parallel access mode
VxFS can run in single instance mode or in a parallel access/cluster file system mode. This latter mode allows for multiple servers (also known as cluster nodes) to simultaneously access the same file system. When run in this mode, VxFS is referred to as Veritas Cluster File System. Cluster File System provides cache coherency and POSIX compliance across nodes, so that data changes are atomically seen by all cluster nodes simultaneously. Because Cluster File System shares the same binaries and same on-disk layout as single instance VxFS, moving between cluster and single instance mode is straightforward.
References
- ^ Incrementally restoring a mass storage device to a prior state (2005-03-22). Retrieved on 2007-11-21.
- ^ Donna Yobs (2000-04-10). Post in the veritas-vx mailing list explaining the differences between JFS and OJFS. Retrieved on 2007-11-21.
- ^ VERITAS Foundation Suite and Foundation Suite HA 3.5. Veritas. Retrieved on 2007-11-21.
- ^ 6th International Linux Kongress (1999-09-09). Retrieved on 2007-11-21.
- ^ Dan Koren (1999-06-01). Re: XFS and journalling filesystems. LKML.org. Retrieved on 2007-11-21.
- ^ Next-Gen File Systems — File under 'futuristic': An overview of the technologies and players — The Heavy Hitters: Veritas. Byte and Switch (2002-11-14). Retrieved on 2007-11-21.
- ^ VERITAS Celebrates 15 Years - Next Big Focus: Grid Computing. SYS-CON (2004-09-14). Retrieved on 2007-11-21.
