VERITAS File System
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. Through an OEM agreement, VxFS is used as the primary filesystem of the HP-UX operating system, although HP-UX calls it JFS. With on-line defragmentation and resize support turned on via license, it is known as OJFS. 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).
According to the vendor, it was the first commercial journaling file system. 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.
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.