An Acronym for Unix FileSystem.

It was originally developed from the first versions of UNIX at AT&T. The FileSystem reached its current status in the 4.x BSD distributions. It it currently used in FreeBSD, NetBSD as well as OpenBSD and the Solaris Operating Environment. The Linux Kernel only includes experimental support.

FreeBSD versions 5.0 introduced UFS2, which allows FileSystem Snapshots, background fscking, as well as support for volumes over 1TB in size.

NetBSD (since 1.5), FreeBSD (since 4.0) and OpenBSD (since 2.3) all employ an addition to UFS called SoftUpdates. SoftUpdates is which is a mechanism that allows a file system to safely use delayed writes for metadata updates. The results are consistent filesystems after powerloss/crash and much improved performance.

See http://www.mckusick.com/softdep/index.html for information