AdvFS
Encyclopedia
AdvFS, also known as Tru64 UNIX Advanced File System, is a file system
developed in the late 1980s to mid 1990s by Digital Equipment Corporation
for their OSF/1 version of the Unix
operating system (later Digital UNIX/Tru64 UNIX
). In June 2008, it was released as open source
under the GNU GPL license.
Its features include:
AdvFS uses a relatively advanced concept of a storage pool (called a file domain) and of logical file systems (called file sets). A file domain is composed of any number of block devices, which could be partitions, LVM
or LSM devices. A file set is a logical file system created in a single file domain. Administrators 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. This was one of the trickier original features to implement because all data or metadata residing on the disk being removed had to first be migrated, online, to other disks, prior to removal.
File sets can be balanced, meaning that file content of file sets be balanced across physical volumes. Particular files in a file set can be striped across available volumes.
Administrators can take a snapshot (or clone) of any active or inactive file set. This allows for easy on-line backups.
Another feature allows administrators to add or remove block devices from a file domain, while the file domain has active users. This add/remove feature allows migration to larger devices or migration from potentially failing hardware without a system shutdown.
AdvFS was developed by DEC engineers in Bellevue, WA (DECwest) that had previously worked on the earlier (cancelled) Mica and Ozix projects there. It was first delivered on the DEC OSF/1 system. Over time, development moved to teams located in Bellevue, WA and Nashua, NH. Versions were always one version number behind the operating system 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 AdvFS v4 had matured to production level stability, with a sufficient set of tools to get administrators out of any kind of trouble. The original team had enough confidence in its log based recovery to release it without an "fsck" style recovery utility on the assumption that the file system journal would always be allocated on mirrored drives.
On June 23, 2008, its source code was released under GNU General Public License
version 2 at SourceForge
in order to be compatible with the Linux kernel license.
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
developed in the late 1980s to mid 1990s by Digital Equipment Corporation
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
for their OSF/1 version of the Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
operating system (later Digital UNIX/Tru64 UNIX
Tru64 UNIX
Tru64 UNIX is a 64-bit UNIX operating system for the Alpha instruction set architecture , currently owned by Hewlett-Packard . Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation , where it was known as Digital UNIX .As its original name suggests, Tru64...
). In June 2008, it was released as open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
under the GNU GPL license.
Its features include:
- a journalJournaling file systemA journaling file system is a file system that keeps track of the changes that will be made in a journal before committing them to the main file system...
to allow for fast crash recovery - undeletionUndeletionUndeletion is a feature for restoring computer files which have been removed from a file system by file deletion. Deleted data can be recovered on many file systems, but not all file systems provide an undeletion feature. Recovering data without an undeletion facility is usually called data...
support - high performance
- dynamic structure that allows an administrator to manage the file system on the flyOn the fly-Colloquial usage:In colloquial use, on the fly means something created when needed. The phrase is used to mean:# something that was not planned ahead# changes that are made during the execution of same activity: ex tempore, impromptu.-Automotive usage:...
- on the fly creation of snapshots
- defragmentation while the domain has active users
AdvFS uses a relatively advanced concept of a storage pool (called a file domain) and of logical file systems (called file sets). A file domain is composed of any number of block devices, which could be partitions, LVM
Logical volume management
In computer storage, logical volume management or LVM provides a method of allocating space on mass-storage devices that is more flexible than conventional partitioning schemes...
or LSM devices. A file set is a logical file system created in a single file domain. Administrators 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. This was one of the trickier original features to implement because all data or metadata residing on the disk being removed had to first be migrated, online, to other disks, prior to removal.
File sets can be balanced, meaning that file content of file sets be balanced across physical volumes. Particular files in a file set can be striped across available volumes.
Administrators can take a snapshot (or clone) of any active or inactive file set. This allows for easy on-line backups.
Another feature allows administrators to add or remove block devices from a file domain, while the file domain has active users. This add/remove feature allows migration to larger devices or migration from potentially failing hardware without a system shutdown.
AdvFS was developed by DEC engineers in Bellevue, WA (DECwest) that had previously worked on the earlier (cancelled) Mica and Ozix projects there. It was first delivered on the DEC OSF/1 system. Over time, development moved to teams located in Bellevue, WA and Nashua, NH. Versions were always one version number behind the operating system 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 AdvFS v4 had matured to production level stability, with a sufficient set of tools to get administrators out of any kind of trouble. The original team had enough confidence in its log based recovery to release it without an "fsck" style recovery utility on the assumption that the file system journal would always be allocated on mirrored drives.
On June 23, 2008, its source code was released under GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
version 2 at SourceForge
SourceForge
SourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...
in order to be compatible with the Linux kernel license.