Comment by tremon

why would you want to embed raid5/6 in the filesystem layer?

There are valid reasons, most having to do with filesystem usage and optimization. Off the top of my head:

- more efficient re-syncs after failure (don't need to re-sync every block, only the blocks that were in use on the failed disk)

- can reconstruct data not only on disk self-reporting, but also on filesystem metadata errors (CRC errors, inconsistent dentries)

- different RAID profiles for different parts of the filesystem (think: parity raid for large files, raid10 for database files, no raid for tmp, N raid1 copies for filesystem metadata)

and for filesystem encryption:

- CBC ciphers have a common weakness: the block size is constant. If you use FS-object encryption instead of whole-FS encryption, the block size, offset and even the encryption keys can be varied across the disk.