Moose File System (MooseFS / MFS) is a fault tolerant, network distributed file system. It spreads data over several physical servers, which are visible to the user as one resource. For standard file operations MooseFS mounted with FUSE acts like other Unix-alike file systems: it has a hierarchical structure; it stores POSIX file attributes; and it supports special files, symbolic links, and hard links. Access to the file system can be limited based on IP address and/or password. It offers high reliability, since several copies of the data can be stored across separate computers. Capacity is dynamically expandable by attaching new computers or disks. Deleted files are retained for a configurable period of time (with a file system level "trash bin"). MooseFS supports coherent snapshots of files, even while the file is being written or accessed.
Lessfs is a high performance inline data deduplicating file system for Linux. Lessfs complies to the POSIX standard and is very useful for backup purposes as well as providing storage for virtual machine images. Although lessfs is a file system that is implemented in user space with FUSE, it offers decent performance. Lessfs is capable of handling data rates up to 350MB/sec. It supports filesystem encryption.
Gfarm is a distributed filesystem, generally used for large scale cluster computing. It's implemented in userland, and can be mounted by FUSE. It utilizes locality of a file to access a data node, and supports Globus GSI for Wide Area Network. Users can explicitly control file replica location on Gfarm. Gfarm can be used as an alternative storage system to HDFS for Hadoop, Samba, MPI-IO, and GridFTP. Monitoring via ZABBIX and Ganglia is also supported.
fsprotect is a set of scripts that combine tmpfs and aufs to make existing filesystems immutable. After the filesystems are protected, everything that is written will be lost when the computer powers off. It is a great tool for testing and for public computers like those in schools, libraries, etc. It is also very easy to use. It is currently available only for Debian-based systems.
Hgfs is a read-only filesystem interface to Mercurial repositories. The interface gives access to the commit message, manifest, and files of each revision, and to .tgz's of each revision (the .tgz's are generated as they are read). The filesystem is a front-end for the Mercurial library that comes with it. All code is written in Limbo, for Inferno.