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* Dynamic inode allocation
 
* Dynamic inode allocation
 
* Writable snapshots, read-only snapshots
 
* Writable snapshots, read-only snapshots
* Subvolumes (separate internal filesystem roots)
+
* [https://btrfs.readthedocs.io/en/latest/Subvolumes.html Subvolumes] (separate internal filesystem roots)
* Checksums on data and metadata (crc32c, xxhash, sha256, blake2b)
+
* [https://btrfs.readthedocs.io/en/latest/Checksumming.html Checksums on data and metadata] (crc32c, xxhash, sha256, blake2b)
 
* [[Compression]] (ZLIB, LZO, ZSTD), heuristics
 
* [[Compression]] (ZLIB, LZO, ZSTD), heuristics
 
* Integrated [[Multiple_Device_Support|multiple device support]]
 
* Integrated [[Multiple_Device_Support|multiple device support]]
Line 56: Line 56:
 
** Single and Dual Parity implementations (experimental, not production-ready)
 
** 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)
 
* 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|incremental backup]]
 
 
* Background scrub process for finding and repairing errors of files with redundant copies
 
* Background scrub process for finding and repairing errors of files with redundant copies
* Online filesystem defragmentation
+
* Online filesystem [https://btrfs.readthedocs.io/en/latest/Defragmentation.html defragmentation]
 
* [[btrfsck|Offline filesystem check]]
 
* [[btrfsck|Offline filesystem check]]
 
* In-place [[Conversion_from_Ext3|conversion]] of existing ext2/3/4 and reiserfs 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]]
* Send/receive of subvolume changes
+
* [file:///home/ds/x/g/btrfs-progs/Documentation/_build/html/Send-receive.html Send/receive] of subvolume changes, efficient incremental filesystem mirroring and [[Incremental_Backup|backup]]
** 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
+
* [https://btrfs.readthedocs.io/en/latest/Swapfile.html Swapfile] support
 
* [[Tree-checker]], post-read and pre-write metadata verification
 
* [[Tree-checker]], post-read and pre-write metadata verification
 +
* [[Zoned]] mode support (SMR/ZBC/ZNS friendly allocation)
 +
* fsverity integration
  
 
=== Features by kernel version ===
 
=== Features by kernel version ===
As part of the changelog you can also review
 
  
 
* [[Changelog#By_feature|features by kernel version]]
 
* [[Changelog#By_feature|features by kernel version]]
Line 76: Line 75:
 
=== Features Currently in Development or Planned for Future Implementation ===
 
=== Features Currently in Development or Planned for Future Implementation ===
  
* SMR (zoned block device) support
 
 
* DAX/persistent memory support
 
* DAX/persistent memory support
 
* The file/directory -level encryption support (fscrypt)
 
* The file/directory -level encryption support (fscrypt)
 +
 +
=== Documentation ===
 +
 +
* https://btrfs.readthedocs.org or https://btrfs.rtfd.io
 +
 
</div>
 
</div>
  
 
<!-- Documentation Block -->
 
<!-- Documentation Block -->
 
<div style="margin:0; margin-top:10px; margin-right:10px; border:1px solid #dfdfdf; padding:0 1em 1em 1em; background-color:#fffff0; align:right; ">
 
<div style="margin:0; margin-top:10px; margin-right:10px; border:1px solid #dfdfdf; padding:0 1em 1em 1em; background-color:#fffff0; align:right; ">
 +
 
== Documentation ==
 
== Documentation ==
  
Line 102: Line 106:
  
 
* "[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]
 
 
* [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://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://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]
 
* [https://wiki.archlinux.org/index.php/Btrfs Btrfs Wiki page] on the [https://wiki.archlinux.org/ Arch Linux Wiki]
 
* [https://wiki.archlinux.org/index.php/Btrfs Btrfs Wiki page] on the [https://wiki.archlinux.org/ Arch Linux Wiki]
* [http://www.funtoo.org/BTRFS_Fun BTRFS Fun Wiki page] on the [http://www.funtoo.org/ Funtoo Wiki]
 
 
* [http://marc.merlins.org/perso/btrfs/post_2014-05-21_My-Btrfs-Talk-at-Linuxcon-JP-2014.html Marc MERLIN's Btrfs talk at Linuxcon JP 2014] which gives an overview of Btrfs, best practices, and its more interesting features.
 
* [http://marc.merlins.org/perso/btrfs/post_2014-05-21_My-Btrfs-Talk-at-Linuxcon-JP-2014.html Marc MERLIN's Btrfs talk at Linuxcon JP 2014] which gives an overview of Btrfs, best practices, and its more interesting features.
  
 
=== Manual pages ===
 
=== Manual pages ===
  
* Manual pages generated from git ([[:Category:Manpage|complete list]]):
+
* Manual pages generated from git ([https://btrfs.readthedocs.io/en/latest/man-index.html complete list]):
** [[Manpage/btrfs|btrfs]] — main administration tool
+
** [https://btrfs.readthedocs.io/en/latest/btrfs.html btrfs] — main administration tool
** [[Manpage/mkfs.btrfs|mkfs.btrfs]] — creating the filesystem
+
** [https://btrfs.readthedocs.io/en/latest/mkfs.btrfs.html mkfs.btrfs] — creating the filesystem
** [[Manpage/btrfs-check|btrfs check]] — repairing file systems
+
** [https://btrfs.readthedocs.io/en/latest/btrfs-check.html btrfs check] — repairing file systems
** [[Manpage/btrfs-convert|btrfs-convert]] — tool to convert in-place from ext2/3/4 filesystems to btrfs. For a greater detail of how the algorithm works, please see the [[Conversion from Ext3]] page.
+
** [https://btrfs.readthedocs.io/en/latest/btrfs-convert.html btrfs-convert] — tool to convert in-place from ext2/3/4 filesystems to btrfs. For a greater detail of how the algorithm works, please see the [[Conversion from Ext3]] page.
  
 
* Original wiki documentation (obsolete, will be removed)
 
* Original wiki documentation (obsolete, will be removed)
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== News ==
 
== News ==
  
''' btrfs-progs v5.10.1 (Feb 2021) '''
+
''' New location for documentation '''
  
* static build works again
+
The new place for documentation will be at https://btrfs.readthedocs.org or https://btrfs.rtfd.io , wiki contents is going to be migrated
* libmount 2.24+ required, not available on Cent OS 7 and the like (fix planned)
+
  
''' btrfs-progs v5.10 (Jan 2021) '''
+
''' IRC channel at libera.chat '''
  
* scrub status:
+
The #btrfs channel is at [https://libera.chat libera.chat], matrix.org bridge works (persistent room #btrfs:matrix.org).
** print percentage of progress
+
 
** add size unit options
+
''' btrfs-progs v5.16 (Jan 2022) '''
* fi usage: also print free space from statfs
+
* rescue: new subcommand clear-uuid-tree to fix failed mount due to bad uuid subvolume keys, caught by tree-checker                                                                                                                                                                           
* convert: copy full 64 bit timestamp from ext4 if availalble
+
* fi du: skip inaccessible files
* check:
+
* prop: properly resolve to symlink targets
** add ability to repair extent item generation
+
* send, receive: fix crash after parent subvolume lookup errors
** new option to remove leftovers from inode number cache (-o inode_cache)
+
* build:
* check for already running exclusive operation (balance, device add/...) when starting one
+
** fix build on 5.12+ kernels due to changes in linux/kernel.h
* preliminary json output support for 'device stats'
+
** fix build on musl with old kernel headers
* fixes:
+
* other:
** subvolume set-default: id 0 correctly falls back to toplevel
+
** error handling fixes, cleanups, refactoring
** receive: align internal buffer to allow fast CRC calculation
+
** extent tree v2 preparatory work
** logical-resolve: distinguish -o subvol and bind mounts
+
** lots of RST documentation updates (last release with asciidoc sources), https://btrfs.readthedocs.io
* build: new dependency libmount
+
 
* other
+
''' linux v5.16 (Jan 2022) '''
** doc fixes and updates
+
 
** new tests
+
Related projects: kernel port of zstd 1.4.10 also [https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c8c109546a19613d323a319d0c921cb1f317e629 released] in 5.16
** ci on gitlab temporarily disabled
+
 
** debugging output enhancements
+
Performance related:
 +
* misc small inode logging improvements (+3% throughput, -11% latency on sample dbench workload)
 +
* more efficient directory logging: bulk item insertion, less tree searches and locking
 +
* speed up bulk insertion of items into a b-tree, which is used when logging directories, when running delayed items for directories (fsync and transaction commits) and when running the slow path (full sync) of an fsync (bulk creation run time -4%, deletion -12%)
 +
 
 +
Core:
 +
* continued subpage support
 +
** make defragmentation work
 +
** make compression write work
 +
* zoned mode
 +
** support ZNS (zoned namespaces), zone capacity is number of usable blocks in each zone
 +
** add dedicated block group (zoned) for relocation, to prevent out of order writes in some cases
 +
** greedy block group reclaim, pick the ones with least usable space first
 +
* preparatory work for send protocol updates
 +
* error handling improvements
 +
* cleanups and refactoring
  
''' 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
 
 
</div>
 
</div>
  
 
<!-- Changelog Block -->
 
<!-- Changelog Block -->
 
<div style="margin:0; margin-top:10px; border:1px solid #dfdfdf; padding: 0em 1em 1em 1em; background-color:#dfefdf; align:left; margin-top:10px">
 
<div style="margin:0; margin-top:10px; border:1px solid #dfdfdf; padding: 0em 1em 1em 1em; background-color:#dfefdf; align:left; margin-top:10px">
 +
 
== Changelog ==
 
== Changelog ==
  
Line 272: Line 277:
 
* 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 [https://libera.chat libera.chat] in the channel [irc://irc.libera.chat:6667/btrfs #btrfs]
 
** Reporting bugs:
 
** 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 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''.
Line 284: Line 289:
 
<!-- Wiki Block -->
 
<!-- Wiki Block -->
 
<div style="margin:0; margin-top:10px; border:1px solid #dfdfdf; padding: 0em 1em 1em 1em; background-color:#dfefdf; align:left; margin-top:10px">
 
<div style="margin:0; margin-top:10px; border:1px solid #dfdfdf; padding: 0em 1em 1em 1em; background-color:#dfefdf; align:left; margin-top:10px">
 +
 
== Wiki accounts, editing ==
 
== Wiki accounts, editing ==
  

Revision as of 12:18, 13 January 2022

btrfs

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. Its main features and benefits are:

  • Snapshots which do not make the full copy of files
  • RAID - support for software-based RAID 0, RAID 1, RAID 10
  • Self-healing - checksums for data and metadata, automatic detection of silent data corruptions

Development of Btrfs started in 2007. Since that time, Btrfs is a part of the Linux kernel and is under active development.

Jointly developed at multiple companies, Btrfs is licensed under the GPL and open for contribution from anyone.

List of companies using btrfs in production.

Development and Issue Reporting

For feature status, please refer to the Status page.

The Btrfs code base is stable. However, new features are still under development. Every effort is made to ensure that it remains stable and fast at 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.

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.

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.

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)
  • 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
  • [file:///home/ds/x/g/btrfs-progs/Documentation/_build/html/Send-receive.html Send/receive] of subvolume changes, efficient incremental filesystem mirroring and backup
  • Batch, or out-of-band deduplication (happens after writes, not during)
  • Swapfile support
  • Tree-checker, post-read and pre-write metadata verification
  • Zoned mode support (SMR/ZBC/ZNS friendly allocation)
  • fsverity integration

Features by kernel version

Features Currently in Development or Planned for Future Implementation

  • DAX/persistent memory support
  • The file/directory -level encryption support (fscrypt)

Documentation

Documentation

Guides and usage information

External Btrfs Documentation / Guides

Links to Btrfs documentation of various Linux distributions:

Manual pages

  • Original wiki documentation (obsolete, will be removed)

Developer documentation

  • Development setup - how to build btrfs from sources and prepare a development environment
  • 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

News

New location for documentation

The new place for documentation will be at https://btrfs.readthedocs.org or https://btrfs.rtfd.io , wiki contents is going to be migrated

IRC channel at libera.chat

The #btrfs channel is at libera.chat, matrix.org bridge works (persistent room #btrfs:matrix.org).

btrfs-progs v5.16 (Jan 2022)

  • rescue: new subcommand clear-uuid-tree to fix failed mount due to bad uuid subvolume keys, caught by tree-checker
  • fi du: skip inaccessible files
  • prop: properly resolve to symlink targets
  • send, receive: fix crash after parent subvolume lookup errors
  • build:
    • fix build on 5.12+ kernels due to changes in linux/kernel.h
    • fix build on musl with old kernel headers
  • other:
    • error handling fixes, cleanups, refactoring
    • extent tree v2 preparatory work
    • lots of RST documentation updates (last release with asciidoc sources), https://btrfs.readthedocs.io

linux v5.16 (Jan 2022)

Related projects: kernel port of zstd 1.4.10 also released in 5.16

Performance related:

  • misc small inode logging improvements (+3% throughput, -11% latency on sample dbench workload)
  • more efficient directory logging: bulk item insertion, less tree searches and locking
  • speed up bulk insertion of items into a b-tree, which is used when logging directories, when running delayed items for directories (fsync and transaction commits) and when running the slow path (full sync) of an fsync (bulk creation run time -4%, deletion -12%)

Core:

  • continued subpage support
    • make defragmentation work
    • make compression write work
  • zoned mode
    • support ZNS (zoned namespaces), zone capacity is number of usable blocks in each zone
    • add dedicated block group (zoned) for relocation, to prevent out of order writes in some cases
    • greedy block group reclaim, pick the ones with least usable space first
  • preparatory work for send protocol updates
  • error handling improvements
  • cleanups and refactoring

Source code download

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

Articles, presentations, podcasts

Historical resources

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

Articles, presentations, podcasts

Project information/Contact

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.

Personal tools