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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.
+
'''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 and LZO)
+
* [[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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* Online filesystem defragmentation
 
* Online filesystem defragmentation
 
* [[btrfsck|Offline filesystem check]]
 
* [[btrfsck|Offline filesystem check]]
−
* In-place [[Conversion_from_Ext3|conversion]] of existing ext3/4 file systems
+
* In-place [[Conversion_from_Ext3|conversion]] of existing ext2/3/4 and reiserfs file systems
 
* [[Seed-device|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.
 
* [[Seed-device|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]]
 
* Subvolume-aware [[quota support]]
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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
+
* SMR (zoned block device) support
−
* Object-level mirroring and striping
+
* DAX/persistent memory support
−
* Alternative checksum algorithms
+
* The file/directory -level encryption support (fscrypt)
−
* In-band deduplication (happes during writes)
+
−
** [https://btrfs.wiki.kernel.org/index.php/Design_notes_on_dedupe In-band dedupe design document]
+
−
** [https://btrfs.wiki.kernel.org/index.php/User_notes_on_dedupe How to use in-band dedupe]
+
−
* Other compression methods ([[Project_ideas#Compression_enhancements|LZ4]])
+
−
* Hot data tracking and moving to faster devices (currently being pushed as a generic feature available through VFS)
+
  
−
== News and Changelog ==
+
== News ==
  
−
'''Wiki update'''
+
''' btrfs-progs v5.10 (Jan 2021) '''
  
−
[[Status#Free_space_tree|Status]]: free space tree promoted to orange level
+
* scrub status:
 +
** print percentage of progress
 +
** add size unit options
 +
* fi usage: also print free space from statfs
 +
* convert: copy full 64 bit timestamp from ext4 if availalble
 +
* check:
 +
** add ability to repair extent item generation
 +
** new option to remove leftovers from inode number cache (-o inode_cache)
 +
* check for already running exclusive operation (balance, device add/...) when starting one
 +
* preliminary json output support for 'device stats'
 +
* fixes:
 +
** subvolume set-default: id 0 correctly falls back to toplevel
 +
** receive: align internal buffer to allow fast CRC calculation
 +
** logical-resolve: distinguish -o subvol and bind mounts
 +
* build: new dependency libmount
 +
* other
 +
** doc fixes and updates
 +
** new tests
 +
** ci on gitlab temporarily disabled
 +
** debugging output enhancements
  
 +
''' linux v5.10 (Dec 2020) '''
 +
* hilights
 +
** performance improvements in fsync (dbench workload: higher throughput, lower latency)
 +
** sysfs exports current exclusive operataion (balance, resize, device add/del/...)
 +
** sysfs exports supported send stream version
 +
* core
 +
** direct io uses iomap infrastructure (no more ''struct buffer_head'')
 +
** space reservations for data now use ticket infrastructure
 +
** cleanups, refactoring, preparatory work
 +
** error handling improvements
 +
** fixes
  
−
'''Linux v4.9 (Dec 2016)'''
+
''' linux v5.9 (Oct 2020) '''
−
* improved performance of extent sharing detection in FIEMAP
+
* hilights
−
* fixes:
+
** add mount option ''rescue'' to unify options for various recovery tasks on a mounted filesystems
−
** device delete hang at the end of the operation
+
** mount option ''inode_cache'' is deprecated and will be removed in 5.11
−
** free space tree bitmap endianity fixed on big-endian machines
+
** removed deprecated options ''alloc_start'' and ''subvolrootid''
−
** parallel incremental send and balance issue fixed
+
** sysfs exports information about qgroups and relations
−
** cloning ioctl can be interrupted by a fatal signal
+
** FS_INFO ioctl exports more information from the filesystem (notably type of checksum)
−
* other stability fixes or cleanups
+
** running balance detects Ctrl-C too
 +
** performance improvements in fsync
 +
** mount-time prefetch of chunk tree
  
−
''' btrfs-progs v4.8.5 (Nov 2016)'''
+
== Changelog ==
  
−
* receive: fix detection of end of stream (error reported even for valid streams)
+
Read about past releases in the separate [[Changelog]] page
−
* other:
+
−
** added test for the receive bug
+
−
** fix linking of library-test
+
  
−
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]]
+
* [[Changelog#By_version_.28linux_kernel.29|kernel changes for each release]]
−
* [[Changelog#By_version_.28btrfs-progs.29|btrfs-progs]]
+
* [[Changelog#By_version_.28btrfs-progs.29|btrfs-progs changes for each release]]
  
 
== Documentation ==
 
== Documentation ==
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* [[Getting started]] — first steps, distributions with btrfs support
 
* [[Getting started]] — first steps, distributions with btrfs support
−
** [[Mount options]]
+
** [[Manpage/btrfs(5)#MOUNT_OPTIONS|Mount options]]
 
* [[FAQ]] — About the btrfs project and filesystem
 
* [[FAQ]] — About the btrfs project and filesystem
 
* [[UseCases]] — Recipes for how to do stuff with btrfs
 
* [[UseCases]] — Recipes for how to do stuff with btrfs
 
* [[SysadminGuide]] — A more in-depth guide to btrfs's concepts and a bit of its internals, to answer all those "but what ''is'' a subvolume?" kind of questions.
 
* [[SysadminGuide]] — A more in-depth guide to btrfs's concepts and a bit of its internals, to answer all those "but what ''is'' a subvolume?" kind of questions.
 
* [[Using Btrfs with Multiple Devices|Multiple devices]] – A guide to the RAID features of Btrfs
 
* [[Using Btrfs with Multiple Devices|Multiple devices]] – A guide to the RAID features of Btrfs
−
* [[Conversion_from_Ext3|Conversion from Ext3 and Ext4]]
+
* [[Conversion_from_Ext3|Conversion from Ext3 and Ext4]] or reiserfs
 
* [[Problem FAQ]] — Commonly-encountered problems and solutions.
 
* [[Problem FAQ]] — Commonly-encountered problems and solutions.
 
** [[Gotchas]] — lists known bugs and issues, but not necessarily solutions.
 
** [[Gotchas]] — lists known bugs and issues, but not necessarily solutions.
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* "[https://docs.oracle.com/cd/E37670_01/E37355/html/ol_btrfs.html The Btrfs File System]" chapter in the [https://docs.oracle.com/cd/E37670_01/E37355/html/index.html Oracle Linux 6 Administrator's Solutions Guide]
 
* "[https://docs.oracle.com/cd/E37670_01/E37355/html/ol_btrfs.html The Btrfs File System]" chapter in the [https://docs.oracle.com/cd/E37670_01/E37355/html/index.html Oracle Linux 6 Administrator's Solutions Guide]
 
* Oracle Linux [https://wikis.oracle.com/display/oraclelinux/Hands-on+lab+-+Storage+Management+with+Btrfs Hands-on lab - Storage Management with Btrfs]
 
* Oracle Linux [https://wikis.oracle.com/display/oraclelinux/Hands-on+lab+-+Storage+Management+with+Btrfs Hands-on lab - Storage Management with Btrfs]
−
* [https://www.suse.com/documentation/sles11/stor_admin/data/sec_filesystems_major.html Major File Systems in Linux] chapter in the [https://www.suse.com/documentation/sles11/stor_admin/data/bookinfo.html SLES 11 Storage Administration Guide]
+
* [https://documentation.suse.com/sles/15-GA/single-html/SLES-storage/#sec-filesystems-major-btrfs Major File Systems in Linux] chapter in the [https://documentation.suse.com/en-us/sles/15-GA/single-html/SLES-storage/ SLES 15 Storage Administration Guide]
 
* [https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-btrfs.html Btrfs] chapter in the [https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ Red Hat Enterprise Linux 6 Storage Administration Guide]
 
* [https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-btrfs.html Btrfs] chapter in the [https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ Red Hat Enterprise Linux 6 Storage Administration Guide]
 
* [https://help.ubuntu.com/community/btrfs Btrfs Wiki page] on the [https://help.ubuntu.com/community Ubuntu Community Help Wiki]
 
* [https://help.ubuntu.com/community/btrfs Btrfs Wiki page] on the [https://help.ubuntu.com/community Ubuntu Community Help Wiki]
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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
+
* [[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''.
+
** 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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=== Developer documentation ===
 
=== Developer documentation ===
  
 +
* [https://github.com/btrfs/btrfs-dev-docs Developer documentation on Github] - collection of documents describing internals of BTRFS
 
* [[Developer's FAQ]] — hints and answers for contributors and developers, general information about patch formatting
 
* [[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)
 
* [[Development notes]] — notes, hints, checklists for specific implementation tasks (eg. adding new ioctls)
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* [[ENOSPC]] — Current ENOSPC design issues
 
* [[ENOSPC]] — Current ENOSPC design issues
 
* [[Design_notes_on_Send/Receive]] — notes from initial impelentation, protocol V2 updates draft
 
* [[Design_notes_on_Send/Receive]] — notes from initial impelentation, protocol V2 updates draft
 +
* [[Qgroups status quo]] - notes on some qgroups observations/pain points
  
 
* [[Debugging Btrfs with GDB]]
 
* [[Debugging Btrfs with GDB]]
 
* [[Writing patch for btrfs]]
 
* [[Writing patch for btrfs]]
 
* [[Btree_Items]] - Mapping from Btrfs key to item-data
 
* [[Btree_Items]] - Mapping from Btrfs key to item-data
 +
* [[Resolving_Extent_Backrefs]] - How back references are resolved to root owners
  
 
* Original COW B-tree: Source code in C that implements the COW B-tree algorithms [https://github.com/orodeh/bt 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.
 
* Original COW B-tree: Source code in C that implements the COW B-tree algorithms [https://github.com/orodeh/bt 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.
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==== Source code download ====
 
==== Source code download ====
  
−
* [[Btrfs source repositories]]
+
[[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
+
−
* [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://www.youtube.com/watch?v=U7gXR2L05IU Deploying Btrfs at Facebook Scale] by Josef Bacik at the Open Source Summit 2020 (2020-06-29)
 +
* '''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://www.phoronix.com/scan.php?page=article&item=linux_34_fs&num=1 XFS, Btrfs, EXT4 Battle It Out On Linux 3.4] (Phoronix.com)
 
−
* '''2012-05''' [http://cd34.com/blog/scalability/ext4-xfs-and-btrfs-benchmark-redux/ Ext4, XFS and Btrfs benchmark redux]
 
−
* '''2012-03''' [http://www.phoronix.com/scan.php?page=article&item=linux_btrfs_options&num=1 Testing Out The Btrfs Mount Options On Linux 3.2] (Phoronix.com)
 
−
* '''2012-03''' [http://www.phoronix.com/scan.php?page=article&item=ubuntu_1204_fs&num=1 Ubuntu 12.04 LTS - Benchmarking All The Linux File-Systems] (Phoronix.com)
 
−
* '''2011-12''' [http://btrfs.boxacle.net Btrfs Performance Analysis]
 
−
* '''2011-11''' [http://www.phoronix.com/vr.php?view=16773 Testing The "Pretty Beefy" Btrfs Changes In Linux 3.2] (Phoronix.com)
 
−
* '''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)
 
−
* '''2011-09''' [http://www.phoronix.com/scan.php?page=article&item=btrfs_linux31_ssd&num=1 Testing EXT4 & Btrfs On A Serial ATA 3.0 SSD] (Phoronix.com)
 
−
* '''2011-05''' [http://www.phoronix.com/scan.php?page=article&item=linux_2639_fs&num=1 Linux 2.6.39: XFS Speeds-Up, EXT4 & Btrfs Unchanged] (Phoronix.com)
 
−
* '''2011-03''' [http://www.phoronix.com/scan.php?page=article&item=btrfs_lzo_2638&num=1 Btrfs LZO Compression Performance] (Phoronix.com)
 
−
* '''2010-12''' [http://www.phoronix.com/scan.php?page=article&item=btrfs_space_cache&num=1 Benchmarks Of The Btrfs Space Cache Option] (Phoronix.com) Comparing the performance of Btrfs using the default mount options, using the space_cache mount option, using the compress mount option for Btrfs file compression, and lastly using both the space_cache and compression mount options to benefit from the free space caching and Zlib compression.
 
−
* '''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)
 
−
* '''2010-11''' [http://www.phoronix.com/scan.php?page=article&item=linux_2637_ext4btrfs&num=1 Phoronix: The Linux 2.6.37 Kernel With EXT4 & Btrfs] (Phoronix.com) Comparison between Btrfs and Ext4.
 
−
* '''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.
 
−
* '''2009-05''' [http://www.phoronix.com/scan.php?page=article&item=btrfs_ssd_mode&num=1 Phoronix Test With SSD Mode] (Phoronix.com) This test show that btrfs is slower with ssd option activated. Ssd code has been updated during 2.6.30-rc and is expected to be faster.
 
−
* '''2009-04''' [http://www.phoronix.com/scan.php?page=article&item=btrfs_benchmarks&num=1 Phoronix Performance Test on Fedora 11 Preview] (Phoronix.com) The phoronix workload is mostly CPU based, but they do have a few filesystem benchmarks. Btrfs performs well, but you can see the checksumming and metadata duplication show up on their single disk streaming write workload. dbench in general measures lots of different caching effects, and is not a great measure of everyday performance.
 
−
* '''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.
 
−
* '''2008-04''' [[Multi-device Benchmarks]]
 

Latest revision as of 22:25, 18 January 2021

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

btrfs-progs v5.10 (Jan 2021)

  • scrub status:
    • print percentage of progress
    • add size unit options
  • fi usage: also print free space from statfs
  • convert: copy full 64 bit timestamp from ext4 if availalble
  • check:
    • add ability to repair extent item generation
    • new option to remove leftovers from inode number cache (-o inode_cache)
  • check for already running exclusive operation (balance, device add/...) when starting one
  • preliminary json output support for 'device stats'
  • fixes:
    • subvolume set-default: id 0 correctly falls back to toplevel
    • receive: align internal buffer to allow fast CRC calculation
    • logical-resolve: distinguish -o subvol and bind mounts
  • build: new dependency libmount
  • other
    • doc fixes and updates
    • new tests
    • ci on gitlab temporarily disabled
    • debugging output enhancements

linux v5.10 (Dec 2020)

  • hilights
    • performance improvements in fsync (dbench workload: higher throughput, lower latency)
    • sysfs exports current exclusive operataion (balance, resize, device add/del/...)
    • sysfs exports supported send stream version
  • core
    • direct io uses iomap infrastructure (no more struct buffer_head)
    • space reservations for data now use ticket infrastructure
    • cleanups, refactoring, preparatory work
    • error handling improvements
    • fixes

linux v5.9 (Oct 2020)

  • hilights
    • add mount option rescue to unify options for various recovery tasks on a mounted filesystems
    • mount option inode_cache is deprecated and will be removed in 5.11
    • removed deprecated options alloc_start and subvolrootid
    • sysfs exports information about qgroups and relations
    • FS_INFO ioctl exports more information from the filesystem (notably type of checksum)
    • running balance detects Ctrl-C too
    • performance improvements in fsync
    • mount-time prefetch of chunk tree

[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

  • 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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