HAMMER FS specific wishlist:
cp doesn't duplicate a file, instead it will reuse the existing ondisk data.
transparent per-PFS compression. This could be performed as a background task. In case a file is compressed, it would be nice if it would be possible to access the compressed data, for example to send out web-pages compressed over the wire without having to decompress and recompress again.
filesystem growing and shrinking (growing is partially implemented, but needs some help).
RAID-features: e.g. keep multiple copies of (certain) files on disk (per-PFS setting?). This could also be performed as a background task. In case multiple copies exists, the filesystem would try one after the other in case of a CRC failure.
De-duplication of data: Blocks with same content are stored only once. Could also be performed as a background task.
See also: Ongoing work