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    SubjectRe: [ANNOUNCE] Btrfs: a copy on write, snapshotting FS
    Chris Mason wrote:
    > Hello everyone,
    >
    > After the last FS summit, I started working on a new filesystem that
    > maintains checksums of all file data and metadata. Many thanks to Zach
    > Brown for his ideas, and to Dave Chinner for his help on
    > benchmarking analysis.
    >
    > The basic list of features looks like this:
    >
    > * 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)
    > - Strong integration with device mapper for multiple device support
    > - Online filesystem check
    > * Very fast offline filesystem check
    > - Efficient incremental backup and FS mirroring

    I would also suggest one more feature: support for block level
    de-duplication. I mean:

    1. Ability for Btrfs to have blocks in several files to point to the
    same block on disk

    2. Support for new syscall or IOCTL to de-duplicate as a single
    transaction two or more blocks on disk, i.e. link them to one of them
    and free others

    3. De-de-duplicate blocks on disk, i.e. copy them on write

    I suppose that de-duplication itself would be done by some user space
    process that would scan files, determine blocks with the same data and
    then de-duplicate them by using syscall or IOCTL (2).

    That would be very usable feature, which in most cases would allow to
    shrink occupied disk space on 50-90%.

    Vlad
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