Training Example: Btrfs Project – Review the Data, Give Your Score & Compare to the Real AI Evaluation

[H1] Main Page

From btrfs Wiki

[H1] OBSOLETE CONTENT
This wiki has been archived and the content is no longer updated.
[IMG: 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 it's been part of the Linux kernel and is under active development.
Jointly developed by multiple companies (https://btrfs.readthedocs.io/en/latest/Contributors.html, Btrfs is licensed under the GPL and open for contribution from anyone.
List of companies using btrfs in production.
[H2] 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.
[H2] 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.
[H3] 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
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
Seeding 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 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
[H3] Features by kernel version
features by kernel version https://btrfs.readthedocs.io/en/latest/Feature-by-version.html
[H3] Documentation
https://btrfs.readthedocs.org or https://btrfs.rtfd.io
the #btrfs channel is at libera.chat, matrix.org bridge works (persistent room #btrfs:matrix.org).
[H2] Documentation
[H3] Guides and usage information
Getting started — first steps, distributions with btrfs support
Mount options
FAQ — About the btrfs project and filesystem
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.
Multiple devices – A guide to the RAID features of Btrfs
Conversion from Ext3 and Ext4 or reiserfs
Problem FAQ — Commonly-encountered problems and solutions.
Gotchas — lists known bugs and issues, but not necessarily solutions.
[H3] Manual pages
Manual pages generated from git (complete list):
btrfs — main administration tool
mkfs.btrfs — creating the filesystem
btrfs check — repairing file systems
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)
restore and find-root — utilities to find and restore data from an unmountable filesystem
[H3] Developer documentation
Development setup - how to build btrfs from sources and prepare a development environment
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
Development notes — notes, hints, checklists for specific implementation tasks (eg. adding new ioctls)
Data Structures — detailed on-disk data structures
On-disk Format - Details of data structures written on disk
Trees — detailed in-tree representation of files and directories
Btrfs design — design notes (possibly out of date in places)
Multiple Device Support — design notes
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
Writing patch for btrfs
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 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.
User notes on dedupe — User/tester notes for using in-band deduplication feature
[H2] News
NOTE: this wiki is archived and not updated anymore (02/2023). Contents will be migrated to https://btrfs.readthedocs.io or https://btrfs.docs.kernel.org
[H2] Changelog
Changelogs and other related information are also tracked at https://btrfs.readthedocs.io:
features by kernel version https://btrfs.readthedocs.io/en/latest/Feature-by-version.html
kernel changes for each release
btrfs-progs changes for each release https://btrfs.readthedocs.io/en/latest/CHANGES.html
[H2] Source code download
Btrfs source repositories describes purpose and contents, here are a few quick links:
repository for kernel pull requests: git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git (gitweb)
kernel development repository: git://github.com/kdave/btrfs-devel.git (web access)
kernel development repository (mirror): git://gitlab.com/kdave/btrfs-devel.git (web access)
btrfs-progs development and release repository: git://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/
[H2] Articles, presentations, podcasts
Video: Deploying Btrfs at Facebook Scale by Josef Bacik at the Open Source Summit 2020 (2020-06-29)
Video: btrfs is awesome, except when it isn't by Richard Brown at openSUSE Conferece 2018 (2018-05-25)
Video: btrfs: The Best Filesystem You've Never Heard Of by poiupoiu at PhreakNIC 21 (2017-11-3)
Video TUT91782 Getting the most out of the btrfs filesystem by Thorsthen Kukuk and Jeff Mahoney (SUSECON, 2017)
Video: NYLUG Presents: Chris Mason on Btrfs (May 14th 2015) by Chris Mason at the 192nd meeting of the NYLUG
Video: Why you should consider using btrfs ... like Google does. by Marc Merlin at linux.conf.au 2015. talk slides
Article: Bitrot and atomic COWs: Inside “next-gen” filesystems (ars technica, 2014/01)
Article: Btrfs: Subvolumes and snapshots (LWN.net, 2014/01)
Article: Btrfs: Working with multiple devices (LWN.net, 2013/12)
Article: Btrfs: Getting started (LWN.net, 2013/12)
Article: Btrfs hands on: An extremely cool file system (ZDNet, 2013/11)
Technical report: 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: 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 [1] page. Otherwise, try IBM Research link
[H2] Historical resources
Links to old or obsolete documentation, articles. Kept for historical reasons. Stuff that's more than 3 years old.
[H3] Articles, presentations, podcasts
Marc MERLIN's Btrfs talk at Linuxcon JP 2014 which gives an overview of Btrfs, best practices, and its more interesting features.
Article: A Beginner's Guide To Btrfs (2012-11-26)
Article: How I Use the Advanced Capabilities of Btrfs by Margaret Bierman with Lenz Grimmer (2012-08-11)
Article: How I Got Started with the Btrfs File System for Oracle Linux by Margaret Bierman with Lenz Grimmer (2012-07-11)
Video: Btrfs Filesystem: Status and New Features by Chris Mason at the 2012 Linux Foundation Collaboration Summit (2012-04-05)
Article Btrfs - The Swiss Army Knife Of Storage by Josef Bacik (2012-02)
Video: I Can't Believe This is Butter! A tour of btrfs by Avi Miller at linux.conf.au (2012-01-18)
Article: A btrfs update at LinuxCon Europe on lwn.net (2011-11-02)
Podcast: Podcast with Chris Mason: Btrfs overview and status update (2011-07-13)
Video: The Story So Far by Josef Bacik at LinuxCon Brazil (2010-08-31)
Article: Linux.com Weekend Project: Get Started with Btrfs (2010-10-15)
Webcast: State of "Btrfs" File System for Linux by Chris Mason (2010-08-26) [email registration and flash required]
Article: Valerie Aurora: A short history of btrfs (2009-07-22)
[H2] Project information/Contact
Development statistics, contributors, commits — https://btrfs.readthedocs.io/en/latest/Contributors.html#statistics-for-5-x-series
Glossary
Contact information:
Btrfs mailing list
IRC on libera.chat in the channel #btrfs, matrix.org bridge works (persistent room #btrfs:matrix.org)
Reporting bugs:
for kernel code see the Bugzilla FAQ, quick tip: use product File System and component btrfs.
for btrfs-progs please use github issues (and not kernel.org bugzilla anymore)
for documentation please use github issues -- report unclear wording, typos, suggest examples, formatting
Project ideas
Cleanup ideas
Userspace tools projects
Retrieved from "https://btrfs.wiki.kernel.org/index.php?title=Main_Page&oldid=33781"

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[H1] Index of /oldwiki/btrfs.wiki.kernel.org/index.php/
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Design_notes_on_Send/ 10-Mar-2023 16:36 -
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Talk:Manpage/ 10-Mar-2023 16:36 -
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Btree_Items.html 10-Mar-2023 16:36 18K
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Btrfs-convert.html 10-Mar-2023 16:36 11K
Btrfs-image.html 10-Mar-2023 16:36 11K
Btrfs_design.html 10-Mar-2023 16:36 35K
Btrfs_mailing_list.html 10-Mar-2023 16:36 14K
Btrfs_source_repositories.html 10-Mar-2023 16:36 19K
Btrfsck.html 10-Mar-2023 16:36 11K
Btrfstune.html 10-Mar-2023 16:36 11K
Category:CodeDoc.html 10-Mar-2023 16:36 11K
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Changelog.html 10-Mar-2023 16:36 85K
Compression.html 10-Mar-2023 16:36 27K
Conversion_from_Ext3.html 10-Mar-2023 16:36 16K
Data_Structures.html 10-Mar-2023 16:36 82K
Debugging_Btrfs_with_GDB.html 10-Mar-2023 16:36 16K
Deduplication.html 10-Mar-2023 16:36 19K
Developer's_FAQ.html 10-Mar-2023 16:36 49K
Development_notes.html 10-Mar-2023 16:36 37K
Development_setup.html 10-Mar-2023 16:36 13K
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Getting_started.html 10-Mar-2023 16:36 22K
Gotchas.html 10-Mar-2023 16:36 24K
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Problem_FAQ.html 10-Mar-2023 16:36 24K
Production_Users.html 10-Mar-2023 16:36 14K
Project_ideas.html 10-Mar-2023 16:36 115K
Qgroups_status_quo.html 10-Mar-2023 16:36 14K
Quota_support.html 10-Mar-2023 16:36 22K
RAID56.html 10-Mar-2023 16:36 10K
Resolving_Extent_Backrefs.html 10-Mar-2023 16:36 61K
Restore.html 10-Mar-2023 16:36 18K
Status.html 10-Mar-2023 16:36 25K
SysadminGuide.html 10-Mar-2023 16:36 42K
Trees.html 10-Mar-2023 16:36 18K
UseCases.html 10-Mar-2023 16:36 38K
User_notes_on_dedupe.html 10-Mar-2023 16:36 25K
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Using_Btrfs_with_Multiple_Devices.html 10-Mar-2023 16:36 27K
Writing_patch_for_btrfs.html 10-Mar-2023 16:36 26K
Zoned.html 10-Mar-2023 16:36 19K

================================================================================
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CPU: 0 PID: 404 Comm: page fault Not tainted 4.0.4 #1
Hardware name: BK-0010-01
RIP: 0010:locate_page+0x404/0xdeadbeef
Code: Bad address at /missing-page
Modules linked in:
- hamster_fs
- idle_procrastination
- questionable_humor
- gif_memes
Process browser (pid: 404, stack limit = 0x7ffc404404)
Stack:
0xdeadbeef 0xbaadf00d 0x40404040
0xfeedface 0x00c0fefe 0x0badcafe
CPU Registers:
EAX: 0xdeadbeef EBX: 0x40404040 ECX: 0xfeedface
EIP: Segmentation Fault: tried to dereference hamster
CR2: 0000000000000000
---[ end trace 404 ]---
Kernel panic: Attempted to fetch non-existent page
Suggested Actions:
- Check address and try again
- Pretend it didn't happen
- Find someone to complain to
_[ Press any key to reboot internet ]_

================================================================================
Oops: 404 NOT FOUND
================================================================================
CPU: 0 PID: 404 Comm: page fault Not tainted 4.0.4 #1
Hardware name: BK-0010-01
RIP: 0010:locate_page+0x404/0xdeadbeef
Code: Bad address at /missing-page
Modules linked in:
- hamster_fs
- idle_procrastination
- questionable_humor
- gif_memes
Process browser (pid: 404, stack limit = 0x7ffc404404)
Stack:
0xdeadbeef 0xbaadf00d 0x40404040
0xfeedface 0x00c0fefe 0x0badcafe
CPU Registers:
EAX: 0xdeadbeef EBX: 0x40404040 ECX: 0xfeedface
EIP: Segmentation Fault: tried to dereference hamster
CR2: 0000000000000000
---[ end trace 404 ]---
Kernel panic: Attempted to fetch non-existent page
Suggested Actions:
- Check address and try again
- Pretend it didn't happen
- Find someone to complain to
_[ Press any key to reboot internet ]_