NAME

       lizardfs, moosefs, mfs - a networking, distributed, highly available file system

DESCRIPTION

       LizardFS is a networking, highly available, distributed file system. It spreads data over
       several physical localisations (servers), which are visible to a user as one resource. For
       standard file operations LizardFS acts as other Unix-alike file systems. It has
       hierarchical structure (directory tree), stores files' attributes (permissions, last
       access and modification times) as well as makes it possible to create special files (block
       and character devices, pipes and sockets), symbolic links (file names pointing to another
       files accessible locally, not necessarily on LizardFS) and hard links (different names of
       files which refer to the same data on LizardFS). Access to the file system can be limited
       basing on IP address and/or password.

       Distinctive features of LizardFS are:

       •   higher reliability (data can be stored in several copies on separate computers)

       •   dynamically expanding disk space by attaching new computers/disks

       •   possibility of storing deleted files for a defined period of time ("trash bin" service
           on a file system level)

       •   possibility of creating snapshot of a file, which means coherent copy of them whole
           file, even while the file is being written.

ARCHITECTURE

       LizardFS installation consists of five types of machines:

       •   master metadata server (or ‘the master’) a managing server - single computer managing
           the whole filesystem, storing metadata for every file (information on size, attributes
           and file localisation(s), including all information about non-regular files, i.e.
           directories, sockets, pipes and devices.

       •   metadata server shadows (or ‘the shadow’) - almost identical to the master, there can
           be any number of those, they work as master metadata server backup and they are ready
           for immediate deployment as new master in case of current master failure.

       •   data servers (any number of commodity servers storing files data and replicating it
           among themselves (if a certain file is supposed to exist in more than one copy).

       •   metadata backup servers - any number of servers, all of which store metadata
           changelogs and periodically downloading base metadata file; it’s easy to run mfsmaster
           process on such machine when primary master stops working.

       •   client computers referring to LizardFS stored files - any number of machines with
           working mfsmount process that communicates with the managing server to receive and
           modify file information and with chunkservers to exchange actual file data.

       Metadata is stored in memory of the managing server and simultaneously is being saved on
       disk (as a periodically updated binary file and immediately updated incremental logs). The
       main binary file as well as the logs are replicated to metaloggers (if present).

       File data is divided to fragments (chunks) of maximum size 64MB each which are stored as
       files on selected disks on data servers (chunkservers). Each chunk is saved on different
       computers in a number of copies equal to a "goal" for the given file.

REPORTING BUGS

       Report bugs to <contact@lizardfs.org>.

COPYRIGHT

       Copyright 2008-2009 Gemius SA, 2013-2015 Skytechnology sp. z o.o.

       LizardFS is free software: you can redistribute it and/or modify it under the terms of the
       GNU General Public License as published by the Free Software Foundation, version 3.

       LizardFS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
       without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
       See the GNU General Public License for more details.

       You should have received a copy of the GNU General Public License along with LizardFS. If
       not, see http://www.gnu.org/licenses/.

SEE ALSO

       mfschunkserver(8), mfsmaster(8), mfsmetalogger(8), mfsmount(1), mfstools(1),
       lizardfs-admin(8)

                                            01/19/2020                                LIZARDFS(7)