TDFS ... or other distributed file system technologies for FreeBSD?

[Ivan Voras]

Greg Troxel wrote:

> I've been playing with Coda for a long time, originally in FreeBSD
> 2.2, 3 and 4, and more recently in NetBSD.  My problems have been all
> correctness issues, both in coda's handling of conflicts and in the
> kernel vfs locking code.  Coda has not yet worked reliably enough that
> I've been worried about performance.  Once you put a network and
> another system in the path, the round trip to user space is not that
> big a deal.

Yes, I suspected that locking will one of the big problems.

> It is truly hard to get the vfs locking issues right (lock one vnode,
> release another, do it in the right order, reference counts, follow
> the rules exactly).  FUSE should (and probably is) taking care of this
> for you.

Yes, but it doesn't support file locking (flock()), which is kind of 
required for serious work.

> The other thing people could do is import puffs and librefuse from
> NetBSD (also originally an SoC project).  puffs is like FUSE, but aims
> to be a richer interface.  librefuse uses puffs to provide a
> FUSE-compatible interface, so you can run FUSE filesystems linked
> against librefuse, and there's no GPL/LGPL code in the base system.

Interesting. I'll look into that. It's too late for SoC but it's nice 
having something like it.

> Porting it to FreeBSD should mostly be straightforward, but I think
> the VFS locking rules have diverged, particularly in how .. locking is
> handled in vfs_lookup.  So making puffs work in FreeBSD will require
> cycles from someone who groks the vfs layer.

Thanks for the information.

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