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Btrfs is a new copy on write (CoW) filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, repair and easy administration. Jointly developed at [[Contributors|multiple companies]], Btrfs is licensed under the GPL and open for contribution from anyone.
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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 [[Contributors|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|production users]] page.
 
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|production users]] page.
  
 
== Stability status ==
 
== Stability status ==
The filesystem [[On-disk_Format|disk format]] is no longer unstable, and it's not expected to change unless there are strong reasons to do so. If there is a format change, file systems with a unchanged format will continue to be mountable and usable by newer kernels.
 
  
The Btrfs code base is under heavy development. Every effort is being made to keep it stable and fast. Due to the fast development speed, the state of development of the filesystem improves noticeably with every new Linux version, so it's recommended to run the most modern kernel possible.
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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.
  
For benchmarks, it's recommended to test the latest stable Linux version, and not any older. If possible, it's also recommendable to test the latest Linux development version. Also, it's recommended to test the [[Mount_options|different options]], f.e. different compression options.
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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.
  
Newly added features may need a few releases to stabilize.
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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.
  
If you have any bug, problems, performance issues or questions while using Btrfs, please email the [[Btrfs mailing list]] (no subscription required). Please report bugs also on [[Problem_FAQ#How_do_I_report_bugs_and_issues.3F|Bugzilla]].
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As with all software, newly added features may need a few releases to stabilize.
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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 [[Problem_FAQ#How_do_I_report_bugs_and_issues.3F|Bugzilla]].
  
 
== Features ==
 
== Features ==
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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.
 
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.
  
'''The main Btrfs features available at the moment include:'''
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=== Major Features Currently Implemented ===
 
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* Extent based file storage
 
* Extent based file storage
 
* 2^64 byte == 16 EiB maximum file size (practical limit is 8 EiB due to Linux VFS)
 
* 2^64 byte == 16 EiB maximum file size (practical limit is 8 EiB due to Linux VFS)
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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)
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* Checksums on data and metadata (crc32c, xxhash, sha256, blake2b)
* [[Compression]] (zlib and LZO)
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* [[Compression]] (ZLIB, LZO, ZSTD), heuristics
* Integrated multiple device support
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* Integrated [[Multiple_Device_Support|multiple device support]]
** File Striping, File Mirroring, File Striping+Mirroring, Striping with Single and Dual Parity implementations
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** File Striping
* 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)
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** File Mirroring
* Efficient [[Incremental Backup]]
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** File Striping+Mirroring
* Background scrub process for finding and fixing errors on files with redundant copies
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** Single and Dual Parity implementations (experimental, not production-ready)
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* 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)
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* Efficient [[Incremental_Backup|incremental backup]]
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* Background scrub process for finding and repairing errors of files with redundant copies
 
* 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
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* 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)
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* Swapfile support
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* [[Tree-checker]], post-read and pre-write metadata verification
  
'''Additional features in development, or planned, include:'''
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=== Features by kernel version ===
 +
As part of the changelog you can also review
 +
 
 +
* [[Changelog#By_feature|features by kernel version]]
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 +
=== Features Currently in Development or Planned for Future Implementation ===
  
* Fast offline filesystem check
 
 
* Online filesystem check
 
* Online filesystem check
 
* Object-level mirroring and striping
 
* Object-level mirroring and striping
* Alternative checksum algorithms
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* In-band deduplication (happens during writes)
* In-band [[deduplication]] (happens during writes)
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* Hot data tracking and moving to faster devices (or provided on the generic VFS layer)
* Other compression methods (snappy, [[Project_ideas#Compression_enhancements|LZ4]])
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* SMR (zoned block device) support
* Hot data tracking and moving to faster devices (currently being pushed as a generic feature available through VFS)
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* DAX/persistent memory support
 +
* The file/directory -level encryption support (fscrypt)
  
 
== News ==
 
== News ==
  
'''btrfs-progs 4.4 (Jan 2016)'''
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''' btrfs-progs v5.7 (Jul 2020) '''
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* mkfs:
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** new option to enable features otherwise enabled at runtime, now implemented for quotas, 'mkfs.btrfs -R quota'
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** fix space accounting for small image, DUP and --rootdir
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** option -A removed
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* check: detect ranges with overlapping csum items
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* fi usage: report correct numbers when plain RAID56 profiles are used
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* convert: ensure the data chunks size never exceed device size
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* libbtrfsutil: update documentation regarding subvolume deletion
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* build: support libkcapi as implementation backend for cryptographic primitives
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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:
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** block group code cleanups
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** build warning fixes
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** more files moved to kernel-shared
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** btrfs-debugfs ported to python 3
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** documentation updates
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** new tests
  
Hilights (see [[Changelog]] for the full change list):
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''' linux v5.7 (May 2020) '''
* mkfs.btrfs --data dup (see also manual page)
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* hilights
* support balance filters added/enhanced in linux 4.4
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** v2 of ioctl to delete subvolumes, allowing to delete by id and more future extensions
** usage=min..max -- enhanced to take range
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** removal of obsolete ioctl flag BTRFS_SUBVOL_CREATE_ASYNC
** stripes=min..max -- new, filter by stripes for raid0/10/5/6
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** more responsive balance cancel
** limit=min..max -- enhanced to take range
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** speedup of extent back reference resolution
* manual pages enhanced (btrfs, mkfs, mount, filesystem, balance)
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** reflink/clone_range works on inline extents
* 'btrfs filesystem usage' works with mixed blockgroups
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* lots of othe core changes, see the [https://git.kernel.org/linus/15c981d16d70e8a5be297fa4af07a64ab7e080ed pull request]
* build: installation to /usr/local
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* build: the 'ar' tool is properly deteced during cross-compilation
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* improved stability on fuzzed/crafted images when reading sys array in superblock
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* debug-tree: option -t understands ids for tree root and chnuk tree
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* check: properly reset nlink of multi-linked file
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* chunk recovery: fix floating point exception
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* chunk recovery: endianity bugfix during rebuild
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* mkfs with 64K pages and nodesize reported superblock checksum mismatch
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'''Linux v4.4 (Jan 2016)'''
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== Changelog ==
  
'''In coreutils 8.24'''
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Read about past releases in the separate [[Changelog]] page
* ''mv'' will attempt ''reflink'' before falling back to standard copy [http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=commit;h=b47231be6813e6cb5305266e391b4bb745f27f13] ([https://lists.gnu.org/archive/html/coreutils-announce/2015-07/msg00000.html release notes])
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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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* [[Getting started]] — first steps, distributions with btrfs support
 
* [[Getting started]] — first steps, distributions with btrfs support
** [[Mount options]]
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** [[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]]
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* [[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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* [[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]]
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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:
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*** 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''.
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*** for btrfs-progs it's either bugzilla or [https://github.com/kdave/btrfs-progs/issues/ github issues]
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*** 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]]
 
* [[Project_ideas#Userspace_tools_projects|Userspace tools projects]]
 
* [[Project_ideas#Userspace_tools_projects|Userspace tools projects]]
  
=== Using the built-in tools ===
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=== Manual pages ===
  
 
* Manual pages generated from git ([[:Category:Manpage|complete list]]):
 
* Manual pages generated from git ([[:Category:Manpage|complete list]]):
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** [[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.
 
** [[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.
  
* Original wiki documenation (obsolete, will be removed)
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* Original wiki documentation (obsolete, will be removed)
 
** [[Restore|restore and find-root]] — utilities to find and restore data from an unmountable filesystem
 
** [[Restore|restore and find-root]] — utilities to find and restore data from an unmountable filesystem
  
 
=== Developer documentation ===
 
=== Developer documentation ===
  
* [[Developer's FAQ]] — hints and answers for contributors and developers
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* [[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
 
* [[Code documentation]] — trees, source files, sample code for manipulating trees
 
* [[Data Structures]] — detailed on-disk data structures
 
* [[Data Structures]] — detailed on-disk data structures
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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
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* [[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.
 +
 +
* Unmerged features
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** In-band (write) time deduplication
 +
*** [[User notes on dedupe]] — User/tester notes for using in-band deduplication feature
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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
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* 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/
 +
 
 +
=== 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.
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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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* '''Article:''' [http://www.zdnet.com/btrfs-hands-on-an-extremely-cool-file-system-7000023734 Btrfs hands on: An extremely cool file system] (ZDNet, 2013/11)
 
* '''Article:''' [http://www.zdnet.com/btrfs-hands-on-an-extremely-cool-file-system-7000023734 Btrfs hands on: An extremely cool file system] (ZDNet, 2013/11)
 
* '''Technical report:''' [http://domino.watson.ibm.com/library/cyberdig.nsf/1e4115aea78b6e7c85256b360066f0d4/9e29fdded06e5de785257c1d005e7e9e!OpenDocument Visualizating Block IO Workloads]. Section six shows a visual comparison of the IO patterns for BTRFS, XFS, and EXT4. Submitted to ACM Transactions on Storage, November 2013.
 
* '''Technical report:''' [http://domino.watson.ibm.com/library/cyberdig.nsf/1e4115aea78b6e7c85256b360066f0d4/9e29fdded06e5de785257c1d005e7e9e!OpenDocument Visualizating Block IO Workloads]. Section six shows a visual comparison of the IO patterns for BTRFS, XFS, and EXT4. Submitted to ACM Transactions on Storage, November 2013.
* '''Paper:''' [http://dl.acm.org/citation.cfm?id=2501623 BTRFS: The Linux B-Tree Filesystem] describing the overall concepts and architecture, appeared in ACM Transactions on Storage, August 2013. Includes a detailed comparison with ZFS. There is a free ACM authorized link, from O. Rodeh's [https://sites.google.com/site/ohadrodehshomepage/research] page. Otherwise, you need a subscription for the ACM library.
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* '''Paper:''' [http://dl.acm.org/citation.cfm?id=2501623 BTRFS: The Linux B-Tree Filesystem] describing the overall concepts and architecture, appeared in ACM Transactions on Storage, August 2013. Includes a detailed comparison with ZFS. There is a free ACM authorized link, from O. Rodeh's [https://sites.google.com/site/ohadrodehshomepage/research] page. Otherwise, try [http://domino.research.ibm.com/library/cyberdig.nsf/papers/6E1C5B6A1B6EDD9885257A38006B6130/$File/rj10501.pdf IBM Research link]
* '''Article:''' [http://www.howtoforge.com/a-beginners-guide-to-btrfs A Beginner's Guide To Btrfs] (2012-11-26)
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* '''Article:''' [http://www.oracle.com/technetwork/articles/servers-storage-admin/advanced-btrfs-1734952.html How I Use the Advanced Capabilities of Btrfs] by Margaret Bierman with Lenz Grimmer (2012-08-11)
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* '''Article:''' [http://www.oracle.com/technetwork/articles/servers-storage-admin/gettingstarted-btrfs-1695246.html How I Got Started with the Btrfs File System for Oracle Linux] by Margaret Bierman with Lenz Grimmer (2012-07-11)
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* '''Article:''' [http://www.funtoo.org/wiki/BTRFS_Fun Btrfs Fun] Wiki page on funtoo.org (2012-05)
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* '''Video:''' [http://video.linux.com/videos/btrfs-filesystem-status-and-new-features Btrfs Filesystem: Status and New Features] by Chris Mason at the 2012 Linux Foundation Collaboration Summit (2012-04-05)
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* '''Article''' [http://static.usenix.org/publications/login/2012-02/openpdfs/Bacik.pdf Btrfs - The Swiss Army Knife Of Storage] by Josef Bacik (2012-02)
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* '''Video:''' [http://www.youtube.com/watch?v=hxWuaozpe2I I Can't Believe This is Butter! A tour of btrfs] by Avi Miller at linux.conf.au (2012-01-18)
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* '''Article:''' [http://lwn.net/Articles/465160/ A btrfs update at LinuxCon Europe] on lwn.net (2011-11-02)
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* '''Podcast:''' [http://feedproxy.google.com/~r/OracleLinux/~3/kRqpaCdTlLg/10491325_Btrfs_071311.mp3 Podcast with Chris Mason: Btrfs overview and status update] (2011-07-13)
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<!--
 
== Benchmarking ==
 
== Benchmarking ==
 
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-->
* '''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)
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* '''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)
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* '''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)
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* '''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)
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* '''2012-05''' [http://cd34.com/blog/scalability/ext4-xfs-and-btrfs-benchmark-redux/ Ext4, XFS and Btrfs benchmark redux]
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* '''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)
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* '''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)
+
  
 
== Historical resources ==
 
== Historical resources ==
Line 191: Line 220:
 
=== Articles, presentations, podcasts ===
 
=== Articles, presentations, podcasts ===
  
 +
* '''Article:''' [http://www.howtoforge.com/a-beginners-guide-to-btrfs A Beginner's Guide To Btrfs] (2012-11-26)
 +
* '''Article:''' [http://www.oracle.com/technetwork/articles/servers-storage-admin/advanced-btrfs-1734952.html How I Use the Advanced Capabilities of Btrfs] by Margaret Bierman with Lenz Grimmer (2012-08-11)
 +
* '''Article:''' [http://www.oracle.com/technetwork/articles/servers-storage-admin/gettingstarted-btrfs-1695246.html How I Got Started with the Btrfs File System for Oracle Linux] by Margaret Bierman with Lenz Grimmer (2012-07-11)
 +
* '''Video:''' [http://video.linux.com/videos/btrfs-filesystem-status-and-new-features Btrfs Filesystem: Status and New Features] by Chris Mason at the 2012 Linux Foundation Collaboration Summit (2012-04-05)
 +
* '''Article''' [http://static.usenix.org/publications/login/2012-02/openpdfs/Bacik.pdf Btrfs - The Swiss Army Knife Of Storage] by Josef Bacik (2012-02)
 +
* '''Video:''' [http://www.youtube.com/watch?v=hxWuaozpe2I I Can't Believe This is Butter! A tour of btrfs] by Avi Miller at linux.conf.au (2012-01-18)
 +
* '''Article:''' [http://lwn.net/Articles/465160/ A btrfs update at LinuxCon Europe] on lwn.net (2011-11-02)
 +
* '''Podcast:''' [http://feedproxy.google.com/~r/OracleLinux/~3/kRqpaCdTlLg/10491325_Btrfs_071311.mp3 Podcast with Chris Mason: Btrfs overview and status update] (2011-07-13)
 
* '''Video:''' [http://vimeo.com/15325851 The Story So Far] by Josef Bacik at LinuxCon Brazil (2010-08-31)
 
* '''Video:''' [http://vimeo.com/15325851 The Story So Far] by Josef Bacik at LinuxCon Brazil (2010-08-31)
 
* '''Article:''' [http://www.linux.com/learn/tutorials/371623-weekend-project-get-started-with-btrfs Linux.com Weekend Project: Get Started with Btrfs] (2010-10-15)
 
* '''Article:''' [http://www.linux.com/learn/tutorials/371623-weekend-project-get-started-with-btrfs Linux.com Weekend Project: Get Started with Btrfs] (2010-10-15)
Line 197: Line 234:
  
 
=== Benchmarks ===
 
=== Benchmarks ===
* '''2011-12''' [http://btrfs.boxacle.net Btrfs Performance Analysis]
+
* '''2019-12''' [https://www.phoronix.com/scan.php?page=article&item=linux54-hdd-raid&num=1 Linux 5.4 EXT4 / XFS / Btrfs RAID Performance On Four HDDs]
* '''2011-11''' [http://www.phoronix.com/vr.php?view=16773 Testing The "Pretty Beefy" Btrfs Changes In Linux 3.2] (Phoronix.com)
+
* '''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)
* '''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 &amp; 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 &amp; 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.
 
* '''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]]
 
 
=== 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.
 

Revision as of 12:21, 24 July 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

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.

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)
  • 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

Features by kernel version

As part of the changelog you can also review

Features Currently in Development or Planned for Future Implementation

  • Online filesystem check
  • Object-level mirroring and striping
  • In-band deduplication (happens during writes)
  • Hot data tracking and moving to faster devices (or provided on the generic VFS layer)
  • SMR (zoned block device) support
  • DAX/persistent memory support
  • The file/directory -level encryption support (fscrypt)

News

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

linux v5.7 (May 2020)

  • hilights
    • v2 of ioctl to delete subvolumes, allowing to delete by id and more future extensions
    • removal of obsolete ioctl flag BTRFS_SUBVOL_CREATE_ASYNC
    • more responsive balance cancel
    • speedup of extent back reference resolution
    • reflink/clone_range works on inline extents
  • lots of othe core changes, see the pull request

Changelog

Read about past releases in the separate Changelog page

Documentation

Guides and usage information

External Btrfs Documentation / Guides

Links to Btrfs documentation of various Linux distributions:

Project information/Contact

Manual pages

  • Original wiki documentation (obsolete, will be removed)

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

Source code download

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

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.

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

Benchmarks

Personal tools