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Introduction
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============
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BTRFS is a modern copy on write (COW) filesystem for Linux aimed at
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implementing advanced features while also focusing on fault tolerance, repair
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and easy administration. Its main features and benefits are:
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* Snapshots which do not make a full copy of the files
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* Built-in volume management, support for software-based RAID 0, RAID 1, RAID 10 and others
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* Self-healing - checksums for data and metadata, automatic detection of silent data corruptions
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Feature overview:
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* Extent based file storage
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* 2\ :sup:`64` byte == 16 EiB :ref:`maximum file size<administration-limits>` (practical limit is 8 EiB due to Linux VFS)
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* :doc:`Space-efficient packing of small files<Inline-files>`
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* Space-efficient indexed directories
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* :ref:`Dynamic inode allocation<administration-flexibility>`
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* :doc:`Writable snapshots, read-only snapshots, subvolumes (separate internal filesystem roots)<Subvolumes>`
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* :doc:`Checksums on data and metadata<Checksumming>` (crc32c, xxhash, sha256, blake2b)
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* :doc:`Compression (ZLIB, LZO, ZSTD), heuristics<Compression>`
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* :doc:`Integrated multiple device support<Volume-management>`:
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* File Striping (like RAID0)
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* File Mirroring (like RAID1 up to 4 copies)
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* File Striping+Mirroring (like RAID10)
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* Single and Dual Parity implementations (like RAID5/6, experimental, not production-ready)
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* SSD/NVMe (flash storage) awareness, :doc:`TRIM/Discard<Trim>` for reporting free blocks for
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reuse and optimizations (e.g. avoiding unnecessary seek optimizations,
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sending writes in clusters.
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* :doc:`Background scrub<Scrub>` process for finding and repairing errors of files with redundant copies
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* :doc:`Online filesystem defragmentation<Defragmentation>`
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* :doc:`Offline filesystem check<btrfs-check>`
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* :doc:`In-place conversion<Convert>` of existing ext2/3/4 and reiserfs filesystems
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* :doc:`Seeding device.<Seeding-device>` Create a (readonly) filesystem that
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acts as a template to seed other Btrfs filesystems. The original filesystem
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and devices are included as a readonly starting point for the new filesystem.
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Using copy on write, all modifications are stored on different devices; the
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original is unchanged.
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* :doc:`Subvolume-aware quota<Qgroups>` support
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* :doc:`Send/receive of subvolume changes<Send-receive>`, efficient
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incremental filesystem mirroring and backup
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* :doc:`Batch, or out-of-band deduplication<Deduplication>` (happens after writes, not during)
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* :doc:`Swapfile support<Swapfile>`
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* :doc:`Tree-checker<Tree-checker>`, post-read and pre-write metadata verification
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* :doc:`Zoned mode support<Zoned-mode>` (SMR/ZBC/ZNS friendly allocation, emulated on non-zoned devices)
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