On Wed, 25 Feb 2009, hooanon05@xxxxxxxxxx wrote: > > The simplest version is with all branches read-only. That gets rid of > > a _huge_ amount of complexity, yet it's still useful in some > > situations. It also deals with a lot of the basic infrastucture > > needed for stacking. > > If you really think it is a better way to get merged into mainline, then > I'll try implement such version. I'd personally be more motivated to review <2000 line chunks (where each step adds new functionality and makes sense in itself), than a 20000 line filesystem all in one. > > And that's when one starts thinking about whether unioning is really > > the right solution. Instead this could be implemented with a special > > filesystem format that only contains deltas to the data, metatata and > > directory tree. It would be much more space efficient, could easily > > handle renames, hard links etc, without all the hacks that > > unionfs/aufs does. > > It sounds like an ODF (on disk format) version of unionfs (while it > seems to be inactive). > At implementing, I don't think it easier to maintain delta of filedata > and metadata. Since aufs has a writable branch in it, it is better and > easier to maintain data in a branch fs. Perhaps it's easier, but copy-up is a very inefficient operation, both in disk space and in time. My personal opinion is that a "delta" filesystem would be cleaner and more useful than a writable union. Writable union filesystems need many hacks to make them useful, such as copy-up, whiteouts, inode number tables, virtual hard links, etc. But that's just a thought, I haven't gone too deeply into this. > If you think there should not be any writable branch in aufs, and all > "write" goes to a new filesystem format, then it is equivalent to a > writable branch, isn't it? Yes, it should be equivalent. > If you say "just a part of write" goes to a new fs, then I don't think > we can support several essential features, for instance mmap. It should be possible to support mmap. Miklos -- 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
