Confira:
LINK: http://oss.oracle.com/projects/btrfs/
Btrfs introduction
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 Btrfs disk format is not yet finalized, and it currently does not handle disk full conditions at all. Things are under heavy development, and Btrfs is not suitable for any uses other than benchmarking and review.
The main Btrfs features include:
* Extent based file storage (264 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)
* Strong integration with device mapper for multiple device support
* Online filesystem check
* Very fast offline filesystem check
* Efficient incremental backup and FS mirroring
Currently the code is in an early implementation phase. It is not optimized and many basic features still need to be added. However, Btrfs does perform well in a number of benchmarks, and it is ready for additional testing, review and analysis.
Benchmarks
Careful benchmarking is a long process, but some numbers are available in the benchmarking section.
Btrfs Design
The Btrfs design paper has details on FS internals.
Status
There is a long list of features that need to be implemented, including handling -ENOSPC, switching from a filesystem wide mutex to a real tree locking scheme, mirroring, striping, and overall fault tolerance. Updates will be posted here as progress is made, but the current code is sufficient to demonstrate performance in a number of workloads.
Install Instructions
Btrfs puts snapshots and subvolumes into the root directory of the FS. This directory can only be changed by btrfsctl right now, and normal filesystem operations do not work on it. The default subvolume is called 'default', and you can create files and directories in mount_point/default.
Btrfs uses libcrc32c in the kernel for file and metadata checksums. You need to compile the kernel with:
CONFIG_LIBCRC32C=m
libcrc32c can be static as well. Once your kernel is setup, typing make in the btrfs module sources will build against the running kernel. When the build is complete:
modprobe libcrc32c
insmod btrfs.ko
The Btrfs utility programs require libuuid to build. This can be found in the e2fsprogs sources, and is usually available as libuuid or e2fsprogs-devel from various distros.
Building the utilities is just make ; make install. The programs go into /usr/local/bin. The commands available are:
* 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
* btrfsck: do a limited check of the FS extent trees.
* debug-tree: print all of the FS metadata in text form. Example:
debug-tree /dev/sda2 >& big_output_file
