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Revision as of 19:55, 18 August 2012
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 Oracle, Red Hat, Fujitsu, Intel, SUSE, STRATO and many others, Btrfs is licensed under the GPL and open for contribution from anyone.
Btrfs is under heavy development, but every effort is being made to keep the filesystem stable and fast. Because of the speed of development, you should run the latest kernel you can (either the latest release kernel from kernel.org, or the latest -rc kernel. Please email the Btrfs mailing list if you have any problems or questions while using Btrfs.
Linux has a wealth of filesystems to choose from, 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:
- Extent based file storage
- 2^64 byte == 16 EiB maximum file size
- 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
- Compression (zlib and LZO)
- Integrated multiple device support
- File Striping, File Mirroring, and File Striping+Mirroring implementations
- 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 fixing errors on files with redundant copies
- Online filesystem defragmentation
- Offline filesystem check
- Conversion of existing ext3/4 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.
Additional features in development, or planned, include:
- Very fast offline filesystem check
- File Striping with Single and Dual Parity
- Object-level mirroring and striping
- Alternative checksum algorithms
- Online filesystem check
- Efficient incremental filesystem mirroring
- Other compression methods (snappy, lz4)
- Hot data tracking and moving to faster devices
- Subvolume-aware quota support
- Send/receive of changes
Coming in Linux 3.6
- subvolume-aware quotas (qgroups)
- support for send/receive between snapshot changes (LWN article)
- atime is not updated on read-only snapshots (LWN article)
- cross-subvolume file clone (aka. reflink)
- remount with no compression possible
- new ioctl to read device readiness status
- speed improvement for concurrent multithreaded reads
- Migration from http://btrfs.ipv5.de
Latest btrfs-progs (c. 26 Mar 2012)
- btrfsck can now repair some forms of filesystem breakage
Enterprise btrfs support (Feb 2012)
- Since February 2012 there are two vendors who support btrfs in their distributions, Oracle and SUSE.
Read about past releases in the Changelog
Articles, presentations, podcasts
- Article: How I Got Started with the Btrfs File System for Oracle Linux by Margaret Bierman with Lenz Grimmer (2012-07-11)
- Paper: draft describing the overall concepts and architecture submitted to ACM TOS (2012-07-10)
- Article: Btrfs Fun Wiki page on funtoo.org (2012-05)
- 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)
- Getting started — first steps, distributions with btrfs support
- FAQ — About the btrfs project and filesystem
- Problem FAQ — Commonly-encountered problems and solutions
- Gotchas — Known bugs and problems
- UseCases — Recipes for how to do stuff with btrfs
- SysadminGuide — A more in-depth guide to btrfs' internals, to answer all those "but what is a subvolume?" kind of questions.
- Changelog — history of changes in linux kernel wrt btrfs
- Using Btrfs with Multiple Devices
- Conversion from Ext3 and Ext4
Source Code Download
- 2012-05 XFS, Btrfs, EXT4 Battle It Out On Linux 3.4
- 2012-05 Ext4, XFS and Btrfs benchmark redux
- 2012-03 Testing Out The Btrfs Mount Options On Linux 3.2
- 2012-03 Ubuntu 12.04 LTS - Benchmarking All The Linux File-Systems
- 2011-12 Btrfs Performance Analysis
- 2011-11 Testing The "Pretty Beefy" Btrfs Changes In Linux 3.2
- 2011-09 Testing EXT4 & Btrfs On A Serial ATA 3.0 SSD
- 2011-05 Linux 2.6.39: XFS Speeds-Up, EXT4 & Btrfs Unchanged
- 2011-03 Btrfs LZO Compression Performance
- 2010-12 Benchmarks Of The Btrfs Space Cache Option 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 SSD Linux benchmarking: Comparing filesystems and encryption method
- 2010-11 Phoronix: The Linux 2.6.37 Kernel With EXT4 & Btrfs Comparison between Btrfs and Ext4.
- 2010-10 One Billion Files Btrfs performs well in comparison to other filesystems, when there are a billion files in the filesystem.
- 2009-05 Phoronix Test With SSD Mode 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 Phoronix Performance Test on Fedora 11 Preview 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 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
- 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
- Unmerged Patches — patches with different features from btrfs mailing list