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 The ones with marked with * are mostly working, and the others are on my todo list. There are more details on the FS design, some benchmarks and download links here: http://oss.oracle.com/~mason/btrfs/ The current status is a very early alpha state, and the kernel code weighs in at a sparsely commented 10,547 lines. I'm releasing now in hopes of finding people interested in testing, benchmarking, documenting, and contributing to the code. I've gotten this far pretty quickly, and plan on continuing to knock off the features as fast as I can. Hopefully I'll manage a release every few weeks or so. The disk format will probably change in some major way every couple of releases. The TODO list has some critical stuff: * Ability to return -ENOSPC instead of oopsing * mmap()ed writes * Fault tolerance, (EIO, bad metadata etc) * Concurrency. I use one mutex for all operations today * ACLs and extended attributes * Reclaim dead roots after a crash * Various other bits from the feature list above And finally, here's a quick and dirty summary of the FS design points: * One large Btree per subvolume * Copy on write logging for all data and metadata * Reference count snapshots are the basis of the transaction system. A transaction is just a snapshot where the old root is immediately deleted on commit * Subvolumes can be snapshotted any number of times * Snapshots are read/write and can be snapshotted again * Directories are doubly indexed to improve readdir speeds So, please give it a try or a look and let me know what you think. -chris - 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
