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Home Directory In CVS

Posted by timothy on from the good-ideas dept.

shamir_k writes "Joey Hess has come up with an innovative solution to a problem we have all faced. He's put his whole home directory in CVS. Not only can he move between multiple computers easily, he also has automatic distributed backups."

1 of 414 comments (clear)

  1. Re:Why just home? by pclminion · · Score: 5, Insightful
    The basic problem with versioning in the file system is deciding when to commit. Do you commit for every byte written? Of course not, that would be a massive waste of time and disk space. Do you commit once for every write() call? That suffers the same problem, because sometimes writes are very small, and you can never predict in advance how large a write will be.

    You can't automatically commit after every xxx bytes of data written, because that means there will be a bunch of intermediate states on disk, most of which are probably bogus (this argument applies to the above two options as well).

    The only thing that even remotely makes sense is to commit on close(), but that doesn't make sense for applications like text editors which keep the file open for the entire duration. You want each SAVE to be a commit, not each CLOSE.

    What this boils down to is that there must be application level support for the commit operation (i.e., a new commit() syscall). The application has to specifically be coded to tell the operating system "Ok, I'm done with the revision, commit this now." And that means every application on the system will have to be tweaked to make the necessary commit calls, not to mention the thought that goes into deciding WHEN it is appropriate to commit. I would wager that a lot of maintainers wouldn't bother to make those changes, and as a result those applications wouldn't support versioning.

    I agree that a versioned file system would kick ass, and there are even some out there already (Google for "versioning filesystems"). But they tend to be special purpose. I don't see how it could be cleanly and transparently integrated into a general purpose system such as Linux.

    Note that I didn't bother to check CiteSeer to see if there is academic work on this before posting this comment. So if anyone knows of any work toward that end, I'm sure a lot of us would appreciate a pointer to it.