>>>>> "Vladislav" == Vladislav Bolkhovitin <vst@xxxxxxxx> writes: >> 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 Vladislav> I would also suggest one more feature: support for block Vladislav> level de-duplication. I mean: Vladislav> 1. Ability for Btrfs to have blocks in several files to Vladislav> point to the same block on disk Yikes! I'd be *very* wary of this feature. It's going to be computationally expensive to do, and it's going to make the entire filesystem more fragile, since now one bit of corruption means that possibly all files with that block are now toast. There would need to be some serious parity checking done here to make me feel confortable with such a system. Vladislav> 2. Support for new syscall or IOCTL to de-duplicate as a Vladislav> single transaction two or more blocks on disk, i.e. link Vladislav> them to one of them and free others Do you want it per-block, or per-file? Vladislav> 3. De-de-duplicate blocks on disk, i.e. copy them on write You mean that if two files are sharing blocks and one gets written to, then the changes are copied to a new block and the pointers updated? Sure, that's a integral part of the concest. Vladislav> I suppose that de-duplication itself would be done by some Vladislav> user space process that would scan files, determine blocks Vladislav> with the same data and then de-duplicate them by using Vladislav> syscall or IOCTL (2). Lots of work... where do you keep the metadata then? In the filesystem? Vladislav> That would be very usable feature, which in most cases Vladislav> would allow to shrink occupied disk space on 50-90%. Maybe. It's reliability I'd be concerned about here. John - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
