Template:Infobox filesystem AdvFS is a proprietary UNIX file system designed to run on Tru64 UNIX. It was created in the early to mid 1990s by Digital Equipment Corporation.

Its features include:

* a journal to allow for fast crash recovery

* high performance

* dynamic structure that allows an administrator to manage the file system on the fly

* on the fly creation of snapshots

AdvFS used a relatively advanced concept of storage pool, called file domain and logical file systems, called file sets. A file domain was comprised of any number of block devices, which could be partitions, LVM or LSM devices. A file set was a logical file system created in one file domain. Administrator can add or remove volumes from an active file domain, providing that there is enough space on the remaining file domain, in case of removal.

File sets can be balanced - file content of file sets be balanced across physical volumes. Particular files in a file set could be striped across available volumes.

Administrator can take a snapshot of any active or inactive file set. Snapshots were called clones. This allowed for easy on-line backups. Most of the advanced features required a special license, which was by no means cheap.

Historically, AdvFS was developed for another operating system and ported to DEC OSF/1 by DEC engineers in Seattle. Over time, development moved to teams located in Seattle and Nashua, NH. Version were 1 version behind the OS version. Thus, DEC OSF/1 v3.2 had AdvFS v2.x, Digital UNIX 4.0 had AdvFS v3.x and Tru64 UNIX 5.x had AdvFS v4.x. It is generally considered that only v4 had matured to production level stability, with sufficient set of tools to get administrator out of any kind of trouble. Author of these lines ran AdvFS on production servers with Oracle RDBMS on all mentioned versions of Tru64 and AdvFS, without real problems.