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authorLinus Torvalds <torvalds@linux-foundation.org>2009-01-09 13:01:38 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-09 13:01:38 -0800
commit73d59314e6ed268d6f322ae1bdd723b23fa5a4ed (patch)
treeec7159b13dfd57739ed840e88a436d8d6f4eee5f /Documentation/filesystems
parent6ddaab20c32af03d68de00e7c97ae8d9820e4dab (diff)
parente293e97e363e419d8a3628a927321e3f75206a0b (diff)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable
* git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable: (864 commits) Btrfs: explicitly mark the tree log root for writeback Btrfs: Drop the hardware crc32c asm code Btrfs: Add Documentation/filesystem/btrfs.txt, remove old COPYING Btrfs: kmap_atomic(KM_USER0) is safe for btrfs_readpage_end_io_hook Btrfs: Don't use kmap_atomic(..., KM_IRQ0) during checksum verifies Btrfs: tree logging checksum fixes Btrfs: don't change file extent's ram_bytes in btrfs_drop_extents Btrfs: Use btrfs_join_transaction to avoid deadlocks during snapshot creation Btrfs: drop remaining LINUX_KERNEL_VERSION checks and compat code Btrfs: drop EXPORT symbols from extent_io.c Btrfs: Fix checkpatch.pl warnings Btrfs: Fix free block discard calls down to the block layer Btrfs: avoid orphan inode caused by log replay Btrfs: avoid potential super block corruption Btrfs: do not call kfree if kmalloc failed in btrfs_sysfs_add_super Btrfs: fix a memory leak in btrfs_get_sb Btrfs: Fix typo in clear_state_cb Btrfs: Fix memset length in btrfs_file_write Btrfs: update directory's size when creating subvol/snapshot Btrfs: add permission checks to the ioctls ...
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+
+ BTRFS
+ =====
+
+Btrfs is a new copy on write filesystem for Linux aimed at
+implementing advanced features while focusing on fault tolerance,
+repair and easy administration. Initially developed by Oracle, Btrfs
+is licensed under the GPL and open for contribution from anyone.
+
+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. Btrfs is under heavy development, and is not suitable for
+any uses other than benchmarking and review. The Btrfs disk format is
+not yet finalized.
+
+The main Btrfs features include:
+
+ * Extent based file storage (2^64 max file size)
+ * Space efficient packing of small files
+ * Space efficient indexed directories
+ * Dynamic inode allocation
+ * Writable snapshots
+ * Subvolumes (separate internal filesystem roots)
+ * Object level mirroring and striping
+ * Checksums on data and metadata (multiple algorithms available)
+ * Compression
+ * Integrated multiple device support, with several raid algorithms
+ * Online filesystem check (not yet implemented)
+ * Very fast offline filesystem check
+ * Efficient incremental backup and FS mirroring (not yet implemented)
+ * Online filesystem defragmentation
+
+
+
+ MAILING LIST
+ ============
+
+There is a Btrfs mailing list hosted on vger.kernel.org. You can
+find details on how to subscribe here:
+
+http://vger.kernel.org/vger-lists.html#linux-btrfs
+
+Mailing list archives are available from gmane:
+
+http://dir.gmane.org/gmane.comp.file-systems.btrfs
+
+
+
+ IRC
+ ===
+
+Discussion of Btrfs also occurs on the #btrfs channel of the Freenode
+IRC network.
+
+
+
+ UTILITIES
+ =========
+
+Userspace tools for creating and manipulating Btrfs file systems are
+available from the git repository at the following location:
+
+ http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-progs-unstable.git
+ git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-progs-unstable.git
+
+These include the following tools:
+
+mkfs.btrfs: create a filesystem
+
+btrfsctl: control program to create snapshots and subvolumes:
+
+ mount /dev/sda2 /mnt
+ btrfsctl -s new_subvol_name /mnt
+ btrfsctl -s snapshot_of_default /mnt/default
+ btrfsctl -s snapshot_of_new_subvol /mnt/new_subvol_name
+ btrfsctl -s snapshot_of_a_snapshot /mnt/snapshot_of_new_subvol
+ ls /mnt
+ default snapshot_of_a_snapshot snapshot_of_new_subvol
+ new_subvol_name snapshot_of_default
+
+ Snapshots and subvolumes cannot be deleted right now, but you can
+ rm -rf all the files and directories inside them.
+
+btrfsck: do a limited check of the FS extent trees.
+
+btrfs-debug-tree: print all of the FS metadata in text form. Example:
+
+ btrfs-debug-tree /dev/sda2 >& big_output_file