Btrfs

infobox filesystem
full_name = Btrfs
name = Btrfs
developer = Oracle Corporation
introduction_os = Linux
introduction_date = June 12, 2007
partition_id =
directory_struct = btree
file_struct = extents
bad_blocks_struct =
max_filename_size = 255 bytes
max_files_no = 2⁶⁴
max_volume_size = 16 EiB
max_file_size = 16 EiB
filename_character_set = All bytes except NUL and '/'
dates_recorded =
date_range =
date_resolution =
forks_streams =
attributes = POSIX
file_system_permissions = POSIX, ACL
compression =
encryption = No
OS = Linux

Btrfs (usually pronounced "Butter FS" [cite video
people = Valerie Henson
title = Chunkfs: Fast file system check and repair
date2 = 2008-01-31
url = http://mirror.linux.org.au/pub/linux.conf.au/2008/Thu/mel8-262.ogg
time = 18m 49s
quote = It's called Butter FS or B-tree FS, but all the cool kids say Butter FS
location = Melbourne, Australia
accessdate = 2008-02-05] [ [http://lwn.net/Articles/267896/ CRFS and POHMELFS [LWN.net ] ] ) is a copy-on-write file system for Linux announced by Oracle in 2007. [ cite web | title = Btrfs: a copy on write, snapshotting FS | author = Chris Mason | date = 2007-06-12 | work = Linux Kernel Mailing List | accessdate = 2007-07-11 | url = http://lkml.org/lkml/2007/6/12/242 ] It aims to replace the ext3 file system while removing a number of its limitations, particularly with respect to file size, total file system size or filesystem checks duration and to bring modern filesystem features not supported by ext3, like writable snapshots, snapshots of snapshots, builtin RAID support, and subvolumes. Btrfs also claims a "focus on fault tolerance, repair and easy administration". [cite web |title=Btrfs wiki Main Page | author=Chris Mason |date=2008-03-12 |accessdate=2008-08-09 |url=http://btrfs.wiki.kernel.org/index.php/Main_Page ]

As of August 2008, Btrfs is still under heavy development and is only intended for testing. Btrfs v0.16 was released August 5, 2008, as free software under the GNU General Public License (GPL). [ [http://thread.gmane.org/gmane.comp.file-systems.btrfs/1006/ Btrfs v0.16 released] ] Btrfs v1.0 (with finalized on-disk format) is scheduled to be released in late 2008. [http://btrfs.wiki.kernel.org/index.php/Development_timeline]

Theodore Ts'o, developer of ext3 and ext4 filesystems, said that Btrfs “has a number of the same design ideas that Reiser4 had” and that “the filesystem format has support for some advanced features that are designed to leapfrog ZFS”. [ cite web | title = Re: reiser4 for 2.6.27-rc1 | author = Theodore Ts'o | date = 2008-08-01 | accessdate = 2008-08-09 | work = Linux Kernel Mailing List | url = http://kerneltrap.org/Linux/Reiser4_Update ]

Features

Btrfs is still in heavy development and many basic features are still missing (like detecting when the disk is full, as of May 2008).The distinctive features (or planned features) of Btrfs include: [Feature list from cite web | title = btrfs and NILFS | author = Jonathan Corbet | date = 2007-06-19 | access date = 2008-08-09 | url = http://lwn.net/Articles/238923/ and cite web | title = Btrfs: a copy on write, snapshotting FS | author = Chris Mason | work = Linux Kernel Mailing List | date = 2007-06-12 | access date = 2008-08-09 | url = http://lwn.net/Articles/237904/ ]

* Space-efficient packing of small files and indexed directories
* Dynamic inode allocation (no maximum number of files set at file system creation time)
* Writable snapshots and snapshots of snapshots
* Subvolumes (multiples and separates internals filesystem roots)
* Object-level mirroring and striping
* Checksums on data and metadata (ie. for strong integrity insurance)
* Copy-on-write logging for all data and metadata
* Strong integration with device mapper for multiple device support, with several built in RAID algorithms
* Online filesystem check and very fast offline filesystem check
* Efficient incremental backup and file system mirroring
* A filesystem can be upgraded from ext3fs to Btrfs
* SSD optimized mode (activated through mount option)

Although Btrfs has no native feature that would make it a distributed or networked filesystem by itself, Oracle is also implementing [http://oss.oracle.com/projects/crfs/ CRFS] ("Coherent Remote File System"), a network filesystem protocol specifically designed and optimized for networked storage on Btrfs.

See also

*List of file systems
*Comparison of file systems
*ext4
*Tux3

References

External links

* [http://btrfs.wiki.kernel.org Btrfs homepage]
* [http://lkml.org/lkml/2007/6/12/242 Initial Btrfs announcement]
* [http://oss.oracle.com/projects/crfs Coherent Remote File System] , built upon btrfs.