Re: DAV on the palm and AVFS

From: Jeff Bone (
Date: Mon Feb 26 2001 - 21:29:19 PST

This gets the "cool hackery of the month" award in my book. Thanks for the
pointer, Steve!



Steve Dossick wrote:

> There was/is a research project at Columbia University called FiST, which is
> a language for describing new kinds of filesystem functionality portably.
> If I recall correctly, you can describe a filesystem and then compile it
> down to a loadable module portably across a number of unices, etc. This was
> being done by Erez Zadok, who is the current maintainer of AMD:
> --
> File System development is very difficult and time consuming. Even small
> changes to existing file systems require deep understanding of kernel
> internals, making the barrier to entry for new developers high. Moreover,
> porting file system code from one operating system to another is almost as
> difficult as the first port. Past proposals to provide extensible
> (stackable) file system interfaces would have simplified the development of
> new file systems. These proposals, however, advocated massive changes to
> existing operating system interfaces and existing file systems; operating
> system vendors and maintainers resist making any large changes to their
> kernels because of stability and performance concerns. As a result, file
> system development is still a difficult, long, and non-portable process.
> The FiST (File System Translator) system combines two methods to solve the
> above problems in a novel way: a set of stackable file system templates for
> each operating system, and a high-level language that can describe stackable
> file systems in a cross-platform portable fashion. Using FiST, stackable
> file systems need only be described once. FiST's code generation tool,
> fistgen, compiles a single file system description into loadable kernel
> modules for several operating systems (currently Solaris, Linux, and
> FreeBSD). In the papers pointed below I (Erez Zadok) show how code size and
> development time are reduced significantly, while imposing a small
> performance overhead of only 1-2%. I achieved these benefits, as well as
> portability, without changing existing operating systems or file system.
> > -----Original Message-----
> > From: []On Behalf Of
> > Justin Mason
> > Sent: Monday, February 26, 2001 10:05 AM
> > To:
> > Cc: Justin Mason; FoRK
> > Subject: Re: DAV on the palm and AVFS
> >
> >
> > This kind of virtual filesystem is one of the really cool things that
> > other OSes have done for a while -- the Acorn Archimedes did it, if I
> > recall correctly, and it's a real Plan 9 concept, so I wouldn't be
> > surprised if it cropped up there too. ;)
> >
> > I also remember a SunOS vfs-over-nfs called "the Waku-Waku filesystem",
> > which allowed browsing of FTP archives, written as a research project
> > about 8 years ago. It was quite limited though, as it could only browse a
> > pre-set list of sites; and it was never ported to Solaris.
> >
> > Anyway, I'm not quite sure why the concept of accessing network resources
> > as a filesystem hasn't really taken off since then... perhaps because they
> > don't map to local FS semantics cleanly and portably enough?

This archive was generated by hypermail 2b29 : Fri Apr 27 2001 - 23:18:43 PDT