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(News and Changelog: Achtung! Achtung!)
(News: linux 5.8)
 
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== Stability status ==
 
== Stability status ==
  
'''For a feature status and stability please refer to the [[Status]] page.''' The filesystem [[On-disk_Format|disk format]] is stable; this means it is not expected to change unless there are very strong reasons to do so. If there is a format change, filesystems which implement the previous disk format will continue to be mountable and usable by newer kernels.
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'''For feature status and stability, please refer to the [[Status]] page.''' The filesystem [[On-disk_Format|disk format]] is stable; this means that it is not expected to change unless there are very strong reasons to do so. If there is a format change, filesystems which implement the previous disk format will continue to be mountable and usable by newer kernels.
  
 
The Btrfs code base is under heavy development. Not only is every effort being made to ensure that it remains stable and fast but to make it more so with each and every commit. This rapid pace of development means that the filesystem improves ''noticeably'' with every new Linux release so it's ''highly'' recommended that users run the most modern kernel possible.
 
The Btrfs code base is under heavy development. Not only is every effort being made to ensure that it remains stable and fast but to make it more so with each and every commit. This rapid pace of development means that the filesystem improves ''noticeably'' with every new Linux release so it's ''highly'' recommended that users run the most modern kernel possible.
  
For benchmarks, it's recommended to test the latest stable Linux version, and not any older, as well as the latest Linux development versions. Also, it's recommended to test the various [[mount options]] such as different compression options.
+
For benchmarks, it's recommended to test the latest stable Linux version, and not any older, as well as the latest Linux development versions. Also, it's recommended to test the various [[Manpage/btrfs(5)#MOUNT_OPTIONS|mount options]] such as different compression options.
  
 
As with all software, newly added features may need a few releases to stabilize.
 
As with all software, newly added features may need a few releases to stabilize.
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* Writable snapshots, read-only snapshots
 
* Writable snapshots, read-only snapshots
 
* Subvolumes (separate internal filesystem roots)
 
* Subvolumes (separate internal filesystem roots)
* Checksums on data and metadata (crc32c)
+
* Checksums on data and metadata (crc32c, xxhash, sha256, blake2b)
* [[Compression]] (zlib, LZO, ZSTD), heuristics
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* [[Compression]] (ZLIB, LZO, ZSTD), heuristics
 
* Integrated [[Multiple_Device_Support|multiple device support]]
 
* Integrated [[Multiple_Device_Support|multiple device support]]
 
** File Striping
 
** File Striping
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** Efficient incremental filesystem mirroring
 
** Efficient incremental filesystem mirroring
 
* Batch, or out-of-band [[deduplication]] (happens after writes, not during)
 
* Batch, or out-of-band [[deduplication]] (happens after writes, not during)
 +
* Swapfile support
 +
* [[Tree-checker]], post-read and pre-write metadata verification
  
 
=== Features by kernel version ===
 
=== Features by kernel version ===
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=== Features Currently in Development or Planned for Future Implementation ===
 
=== Features Currently in Development or Planned for Future Implementation ===
  
* Online filesystem check
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* SMR (zoned block device) support
* Object-level mirroring and striping
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* Alternative checksum algorithms
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* In-band deduplication (happes during writes)
+
** [https://btrfs.wiki.kernel.org/index.php/Design_notes_on_dedupe In-band dedupe design document]
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** [https://btrfs.wiki.kernel.org/index.php/User_notes_on_dedupe How to use in-band dedupe]
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* Hot data tracking and moving to faster devices (or provided on the generic VFS layer)
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* SMR support
+
 
* DAX/persistent memory support
 
* DAX/persistent memory support
 
* The file/directory -level encryption support (fscrypt)
 
* The file/directory -level encryption support (fscrypt)
  
== News and Changelog ==
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== News ==
  
<b>WARNING:</b> kernels <b>4.14.25 - 4.14.27</b> and <b>4.15.8 - 4.15.9</b> on <b>big endian</b> machines
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''' linux v5.8 (Aug 2020) '''
will damage a filesystem after first umount. Little endian machines are unaffected. Please contact upstream developers if your filesystems were affected, the problem can be manually fixed and is only in the superblock, not data or regular metadata.
+
* Hilights:
 +
** speedup dead root detection during orphan cleanup
 +
** send will emit file capabilities after chown
 +
* Core changes:
 +
** improved global block reserve utilization
 +
** direct io cleanups and fixes
 +
** refactored block group reading code
 +
** lots of other core changes see the [https://git.kernel.org/linus/f3cdc8ae116e27d84e1f33c7a2995960cebb73ac pull request]
  
''' btrfs-progs v4.15.1 (Feb 2018) '''
+
''' btrfs-progs v5.7 (Jul 2020) '''
* build
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* mkfs:
** fix build on musl
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** new option to enable features otherwise enabled at runtime, now implemented for quotas, 'mkfs.btrfs -R quota'
** support asciidoctor for doc generation
+
** fix space accounting for small image, DUP and --rootdir
* cleanups
+
** option -A removed
** sync some code with kernel
+
* check: detect ranges with overlapping csum items
** check: move code to own directory, split to more files
+
* fi usage: report correct numbers when plain RAID56 profiles are used
* tests
+
* convert: ensure the data chunks size never exceed device size
** more build tests in travis
+
* libbtrfsutil: update documentation regarding subvolume deletion
** tests now pass with asan and ubsan
+
* build: support libkcapi as implementation backend for cryptographic primitives
** testsuite can be exported and used separately
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* core: global options for verbosity (-v, -q), subcommands -v or -q are aliases and will continue to work but are considered deprecated, current command output is preserved to keep scripts working
 +
* other:
 +
** block group code cleanups
 +
** build warning fixes
 +
** more files moved to kernel-shared
 +
** btrfs-debugfs ported to python 3
 +
** documentation updates
 +
** new tests
  
''' Linux v4.15 (Jan 2018) '''
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== Changelog ==
* new features
+
 
** extend mount options to specify zlib compression level, <i>-o compress=zlib:9</i>
+
Read about past releases in the separate [[Changelog]] page
** v2 of ioctl "extent to inode mapping"
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** populate compression heuristics logic
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** enable indexing for btrfs as lower filesystem in overlayfs
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** speedup page cache readahead during send on large files
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* internal changes
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** more sanity checks of b-tree items when reading them from disk
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** more EINVAL/EUCLEAN fixups, missing BLK_STS_* conversion, other errno or error handling fixes
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** remove some homegrown IO-related logic, that's been obsoleted by core block layer changes (batching, plug/unplug, own counters)
+
** add ref-verify, optional debugging feature to verify extent reference accounting
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** simplify code handling outstanding extents, make it more clear where and how the accounting is done
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** make delalloc reservations per-inode, simplify the code and make the logic more straightforward
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** extensive cleanup of delayed refs code
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* fix send ioctl on 32bit with 64bit kernel
+
  
Read about past releases in the [[Changelog]]
 
 
* [[Changelog#By_feature|features by kernel version]]
 
* [[Changelog#By_feature|features by kernel version]]
* [[Changelog#By_version_.28linux_kernel.29|kernel changes]]
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* [[Changelog#By_version_.28linux_kernel.29|kernel changes for each release]]
* [[Changelog#By_version_.28btrfs-progs.29|btrfs-progs]]
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* [[Changelog#By_version_.28btrfs-progs.29|btrfs-progs changes for each release]]
  
 
== Documentation ==
 
== Documentation ==
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* [[Changelog]] — history of changes in linux kernel wrt btrfs
 
* [[Changelog]] — history of changes in linux kernel wrt btrfs
 
** [[Changelog#By_feature | features added by release]]
 
** [[Changelog#By_feature | features added by release]]
* [[Contributors#Statistics|Development statistics]] — contributors, commits, lines
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* [[Contributors#Statistics_for_5.x_series|Development statistics]] — contributors, commits, lines
 
* [[Glossary]]
 
* [[Glossary]]
 
* Contact information:
 
* Contact information:
 
** [[Btrfs mailing list]]
 
** [[Btrfs mailing list]]
 
** [http://en.wikipedia.org/wiki/Internet_Relay_Chat IRC] on freenode.net in the channel [irc://irc.freenode.net:6667/btrfs #btrfs]
 
** [http://en.wikipedia.org/wiki/Internet_Relay_Chat IRC] on freenode.net in the channel [irc://irc.freenode.net:6667/btrfs #btrfs]
** Reporting bugs: see [[Problem_FAQ#How_do_I_report_bugs_and_issues.3F | the Bugzilla FAQ]] for reporting and finding bugs. Quick tip: use product ''File System'' and component ''btrfs''.
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** Reporting bugs:
 +
*** for kernel code see [[Problem_FAQ#How_do_I_report_bugs_and_issues.3F | the Bugzilla FAQ]], quick tip: use product ''File System'' and component ''btrfs''.
 +
*** for btrfs-progs it's either bugzilla or [https://github.com/kdave/btrfs-progs/issues/ github issues]
 +
*** for read-only documentation exported on wiki eg. manual pages as [https://github.com/kdave/btrfs-progs/issues/ github issues]
 
* [[Project ideas]]
 
* [[Project ideas]]
 
* [[Project_ideas#Cleanup_projects|Cleanup ideas]]
 
* [[Project_ideas#Cleanup_projects|Cleanup ideas]]
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==== Source code download ====
 
==== Source code download ====
  
* [[Btrfs source repositories]]
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[[Btrfs source repositories]] describes purpose and contents, here are a few quick links:
* [http://git.kernel.org/?p=linux/kernel/git/mason/linux-btrfs.git;a=tree;f=fs/btrfs;hb=HEAD Gitweb source viewer] of the main kernel repository
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* [https://git.kernel.org/cgit/linux/kernel/git/kdave/btrfs-progs.git/ Gitweb source viewer] of the userspace tools repository
+
  
=== Wiki editing ===
+
* repository for kernel pull requests: git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git ([https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git gitweb])
 +
* kernel development repository: git://github.com/kdave/btrfs-devel.git ([https://github.com/kdave/btrfs-devel.git web access])
 +
* kernel development repository (mirror): git://gitlabs.com/kdave/btrfs-devel.git ([https://gitlab.com/kdave/btrfs-devel.git web access])
 +
* btrfs-progs development and release repository: git://github.com/kdave/btrfs-progs.git ([https://github.com/kdave/btrfs-progs.git web access])
 +
* released tarballs of btrfs-progs: https://mirrors.edge.kernel.org/pub/linux/kernel/people/kdave/btrfs-progs/
  
The wiki contributions are welcome! Please create an account and wait for approval (this is a necessary spam protection). You can try to catch some of the wiki admins on [[#Project_information.2FContact|IRC]] and expedite the account creation.
+
=== Wiki accounts, editing ===
 +
 
 +
The wiki contributions are welcome! Please create an account and wait for approval (this is a necessary spam protection and we cannot remove it). You can try to catch some of the wiki admins on [[#Project_information.2FContact|IRC]] (or ping user 'kdave' in a query) to expedite the account creation.
 +
 
 +
The registration requires full name for account but it's not mandatory from our perspective. The wiki User and User talk pages are created automatically but removed after account is approved. If you want to use the pages, create them manually, they won't be deleted.
  
 
== Articles, presentations, podcasts ==
 
== Articles, presentations, podcasts ==
 +
* '''Video:''' [https://youtu.be/qHalOdCZO9Q btrfs is awesome, except when it isn't] by Richard Brown at openSUSE Conferece 2018 (2018-05-25)
 +
* '''Video:''' [https://youtu.be/-m01x3gHNjg btrfs: The Best Filesystem You've Never Heard Of] by poiupoiu at PhreakNIC 21 (2017-11-3)
 +
* '''Video''' [https://youtu.be/iwNg_fusT9A TUT91782 Getting the most out of the btrfs filesystem by Thorsthen Kukuk and Jeff Mahoney] (SUSECON, 2017)
 
* '''Video:''' [https://www.youtube.com/watch?v=W3QRWUfBua8 NYLUG Presents: Chris Mason on Btrfs (May 14th 2015)] by Chris Mason at the 192nd meeting of the NYLUG
 
* '''Video:''' [https://www.youtube.com/watch?v=W3QRWUfBua8 NYLUG Presents: Chris Mason on Btrfs (May 14th 2015)] by Chris Mason at the 192nd meeting of the NYLUG
 
* '''Video:''' [https://www.youtube.com/watch?v=6DplcPrQjvA Why you should consider using btrfs ... like Google does.] by Marc Merlin at linux.conf.au 2015. [http://marc.merlins.org/linux/talks/Btrfs-LCA2015/ talk slides]
 
* '''Video:''' [https://www.youtube.com/watch?v=6DplcPrQjvA Why you should consider using btrfs ... like Google does.] by Marc Merlin at linux.conf.au 2015. [http://marc.merlins.org/linux/talks/Btrfs-LCA2015/ talk slides]
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== Benchmarking ==
 
== Benchmarking ==
 
-->
 
-->
 
  
 
== Historical resources ==
 
== Historical resources ==
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* '''Webcast:''' [https://event.on24.com/eventRegistration/EventLobbyServlet?target=registration.jsp&eventid=233161&sessionid=1&key=D0B1D3285FA444C5745C344A1C859CE0&partnerref=banner&sourcepage=register State of "Btrfs" File System for Linux by Chris Mason] (2010-08-26) [email registration and flash required]
 
* '''Webcast:''' [https://event.on24.com/eventRegistration/EventLobbyServlet?target=registration.jsp&eventid=233161&sessionid=1&key=D0B1D3285FA444C5745C344A1C859CE0&partnerref=banner&sourcepage=register State of "Btrfs" File System for Linux by Chris Mason] (2010-08-26) [email registration and flash required]
 
* '''Article:''' [http://lwn.net/Articles/342892/ Valerie Aurora: A short history of btrfs] (2009-07-22)
 
* '''Article:''' [http://lwn.net/Articles/342892/ Valerie Aurora: A short history of btrfs] (2009-07-22)
 
=== Benchmarks ===
 
* '''2012-10''' [http://www.ilsistemista.net/index.php/linux-a-unix/36-btrfs-mount-options-and-virtual-machines-an-in-depth-look.html BTRFS, mount options and virtual machines: an in-depth look] (Ilsistemista.net)
 
* '''2012-06''' [http://www.ilsistemista.net/index.php/linux-a-unix/34-btrfs-ext3-ext4-xfs-and-kvm-virtual-machine-a-host-side-filesystem-comparison.html BTRFS EXT3 EXT4 XFS and KVM virtual machine: a host-side filesystem comparison] (Ilsistemista.net)
 
* '''2012-06''' [http://www.ilsistemista.net/index.php/linux-a-unix/33-btrfs-vs-ext3-vs-ext4-vs-xfs-performance-on-fedora-17.html BTRFS vs EXT3 vs EXT4 vs XFS performance on Fedora 17] (Ilsistemista.net)
 
* '''2012-05''' [http://cd34.com/blog/scalability/ext4-xfs-and-btrfs-benchmark-redux/ Ext4, XFS and Btrfs benchmark redux]
 
* '''2011-12''' [http://btrfs.boxacle.net Btrfs Performance Analysis]
 
* '''2011-10''' [http://www.ilsistemista.net/index.php/linux-a-unix/21-ext3-ext4-xfs-and-btrfs-filesystems-comparison-on-linux-kernel-300.html EXT3 vs EXT4 vs XFS vs BTRFS - filesystems comparison on Linux kernel 3.0.0] (Ilsistemista.net)
 
* '''2010''' [http://www.mayrhofer.eu.org/ssd-linux-benchmark SSD Linux benchmarking: Comparing filesystems and encryption method]
 
* '''2010-11''' [http://www.ilsistemista.net/index.php/linux-a-unix/6-linux-filesystems-benchmarked-ext3-vs-ext4-vs-xfs-vs-btrfs.html EXT3 vs EXT4 vs XFS vs BTRFS linux filesystems benchmark] (Ilsistemista.net)
 
* '''2010-10''' [http://www.linux-mag.com/id/7876 One Billion Files] Btrfs performs well in comparison to other filesystems, when there are a billion files in the filesystem.
 
* '''2008-10''' [http://btrfs.boxacle.net Btrfs performance analysis by Steven Pratt and IBM] The benchmarks from IBM demonstrate some bottlenecks we have in the extent recording on large workloads. We're working on fixes for these.
 

Latest revision as of 10:22, 19 August 2020

Btrfs is a modern copy on write (CoW) filesystem for Linux aimed at implementing advanced features while also focusing on fault tolerance, repair and easy administration. Jointly developed at multiple companies, Btrfs is licensed under the GPL and open for contribution from anyone. Not too many companies have said that they are using Btrfs in production, but we welcome those who can say so on the production users page.

Contents

[edit] Stability status

For feature status and stability, please refer to the Status page. The filesystem disk format is stable; this means that it is not expected to change unless there are very strong reasons to do so. If there is a format change, filesystems which implement the previous disk format will continue to be mountable and usable by newer kernels.

The Btrfs code base is under heavy development. Not only is every effort being made to ensure that it remains stable and fast but to make it more so with each and every commit. This rapid pace of development means that the filesystem improves noticeably with every new Linux release so it's highly recommended that users run the most modern kernel possible.

For benchmarks, it's recommended to test the latest stable Linux version, and not any older, as well as the latest Linux development versions. Also, it's recommended to test the various mount options such as different compression options.

As with all software, newly added features may need a few releases to stabilize.

If you find any behavior you suspect to be caused by a bug, performance issues, or have any questions about using Btrfs, please email the Btrfs mailing list (no subscription required). Please report bugs on Bugzilla.

[edit] Features

Linux has a wealth of filesystems from which to choose, but we are facing a number of challenges with scaling to the large storage subsystems that are becoming common in today's data centers. Filesystems need to scale in their ability to address and manage large storage, and also in their ability to detect, repair and tolerate errors in the data stored on disk.

[edit] Major Features Currently Implemented

  • Extent based file storage
  • 2^64 byte == 16 EiB maximum file size (practical limit is 8 EiB due to Linux VFS)
  • Space-efficient packing of small files
  • Space-efficient indexed directories
  • Dynamic inode allocation
  • Writable snapshots, read-only snapshots
  • Subvolumes (separate internal filesystem roots)
  • Checksums on data and metadata (crc32c, xxhash, sha256, blake2b)
  • Compression (ZLIB, LZO, ZSTD), heuristics
  • Integrated multiple device support
    • File Striping
    • File Mirroring
    • File Striping+Mirroring
    • Single and Dual Parity implementations (experimental, not production-ready)
  • SSD (flash storage) awareness (TRIM/Discard for reporting free blocks for reuse) and optimizations (e.g. avoiding unnecessary seek optimizations, sending writes in clusters, even if they are from unrelated files. This results in larger write operations and faster write throughput)
  • Efficient incremental backup
  • Background scrub process for finding and repairing errors of files with redundant copies
  • Online filesystem defragmentation
  • Offline filesystem check
  • In-place conversion of existing ext2/3/4 and reiserfs file systems
  • Seed devices. Create a (readonly) filesystem that acts as a template to seed other Btrfs filesystems. The original filesystem and devices are included as a readonly starting point for the new filesystem. Using copy on write, all modifications are stored on different devices; the original is unchanged.
  • Subvolume-aware quota support
  • Send/receive of subvolume changes
    • Efficient incremental filesystem mirroring
  • Batch, or out-of-band deduplication (happens after writes, not during)
  • Swapfile support
  • Tree-checker, post-read and pre-write metadata verification

[edit] Features by kernel version

As part of the changelog you can also review

[edit] Features Currently in Development or Planned for Future Implementation

  • SMR (zoned block device) support
  • DAX/persistent memory support
  • The file/directory -level encryption support (fscrypt)

[edit] News

linux v5.8 (Aug 2020)

  • Hilights:
    • speedup dead root detection during orphan cleanup
    • send will emit file capabilities after chown
  • Core changes:
    • improved global block reserve utilization
    • direct io cleanups and fixes
    • refactored block group reading code
    • lots of other core changes see the pull request

btrfs-progs v5.7 (Jul 2020)

  • mkfs:
    • new option to enable features otherwise enabled at runtime, now implemented for quotas, 'mkfs.btrfs -R quota'
    • fix space accounting for small image, DUP and --rootdir
    • option -A removed
  • check: detect ranges with overlapping csum items
  • fi usage: report correct numbers when plain RAID56 profiles are used
  • convert: ensure the data chunks size never exceed device size
  • libbtrfsutil: update documentation regarding subvolume deletion
  • build: support libkcapi as implementation backend for cryptographic primitives
  • core: global options for verbosity (-v, -q), subcommands -v or -q are aliases and will continue to work but are considered deprecated, current command output is preserved to keep scripts working
  • other:
    • block group code cleanups
    • build warning fixes
    • more files moved to kernel-shared
    • btrfs-debugfs ported to python 3
    • documentation updates
    • new tests

[edit] Changelog

Read about past releases in the separate Changelog page

[edit] Documentation

[edit] Guides and usage information

[edit] External Btrfs Documentation / Guides

Links to Btrfs documentation of various Linux distributions:

[edit] Project information/Contact

[edit] Manual pages

  • Original wiki documentation (obsolete, will be removed)

[edit] Developer documentation

  • Developer's FAQ — hints and answers for contributors and developers, general information about patch formatting
  • Development notes — notes, hints, checklists for specific implementation tasks (eg. adding new ioctls)
  • Code documentation — trees, source files, sample code for manipulating trees
  • Data Structures — detailed on-disk data structures
  • Trees — detailed in-tree representation of files and directories
  • Original COW B-tree: Source code in C that implements the COW B-tree algorithms repository. Written by Ohad Rodeh at IBM Research in 2006, and released under a BSD license. This is a reference implementation, that works in user space.
  • Unmerged features
    • In-band (write) time deduplication

[edit] Source code download

Btrfs source repositories describes purpose and contents, here are a few quick links:

[edit] Wiki accounts, editing

The wiki contributions are welcome! Please create an account and wait for approval (this is a necessary spam protection and we cannot remove it). You can try to catch some of the wiki admins on IRC (or ping user 'kdave' in a query) to expedite the account creation.

The registration requires full name for account but it's not mandatory from our perspective. The wiki User and User talk pages are created automatically but removed after account is approved. If you want to use the pages, create them manually, they won't be deleted.

[edit] Articles, presentations, podcasts


[edit] Historical resources

Links to old or obsolete documentation, articles. Kept for historical reasons. Stuff that's more than 3 years old.

[edit] Articles, presentations, podcasts

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