Tux3

Infobox filesystem
name = Tux3
developer = Daniel Phillips
full_name = Tux3
introduction_date = July 23, 2008
introduction_os = Linux 2.6.x
partition_id = 0x83 (MBR)Superblock magic: "TUX3" {0x54, 0x55, 0x58, 0x33}
directory_struct = B-tree
file_struct = B-tree
bad_blocks_struct =
max_file_size = 2^60 bytes (1 EiB)
max_files_no = 2^48
max_filename_size = 255 bytes
max_volume_size = 2^60 bytes (1 EiB)
filename_character_set = All bytes except NUL and '/'
dates_recorded = attribute modification (ctime), modification (mtime), access time (atime), version create
date_range = 40 bits
date_resolution = 1/256 second
forks_streams =
attributes =
file_system_permissions = standard unix
compression =
encryption =
single_instance_storage =
OS = Linux

Tux3 is a versioning filesystem being developed by Daniel Phillips (creator of the H tree directory indexing system, now standard in ext3). [http://www.linuxsymposium.org/2007/view_bio.php?id=2311] . It is a successor to the Tux2 filesystem [http://slashdot.org/features/00/10/13/2117258.shtml] designed by the same author. The structure of Tux3 was first publicized in an email on July 23rd, 2008. [http://lkml.org/lkml/2008/7/23/257] It attempts to avoid traditional journaling by introducing a recovery logic which allows it to recover upon remounting. [http://tux3.org/pipermail/tux3/2008-July/000002.html]

In broad outline, Tux3 is a conventional Unix-style inode/file/directory design with wrinkles. A Tux3 inode table is a btree with versioned attributes at the leaves. A file is an inode attribute that is a btree with versioned extents at the leaves. Directory indexes are mapped into directory file blocks as with HTree. Free space is mapped by a btree with extents at the leaves.

A Tux3 inode is a variable sized object consist of a list of attributes, each labeled by the version at which the attribute was added, changed or removed. The btree index by which inodes are referenced is not versioned. The btree index of a large file is also not versioned, except for the leaves of the index, which contain lists of extents, each labeled by the version at which the referenced file data was added or changed. This style of versioning is essentially the inverse of tree versioning methods used by WAFL, ZFS and Btrfs, where multiple tree roots of an entire filesystem are created in order to express differences between versions of the filesystem. The advantage of Tux3 style versioned entities is that only a few bytes need to be added to represent single changes to inode attributes or to index new versions of file data blocks, compared to some number of index blocks needing to be allocated and written for tree-versioned filesystems.

As of August 2008, Tux3 is only capable of basic file I/O to files.

References

External links

* [http://tux3.org/ Official website]
* [http://www.linuxpromagazine.com/online/news/tux_redux Linux Pro Magazine - Tux Redux]