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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