[TUHS] VFS prior to 1984

Wed Jun 24 06:57:32 AEST 2020

The SunOS one hid the block stuff pretty well.  It had mmap().  

Where it got hairy when I was working on it was block size 4k vs page
size 8k.  And frags, I hate frags.

On Wed, Jun 24, 2020 at 06:38:53AM +1000, Rob Pike wrote:
> For my taste, the various Unix file system switches that I've seen are too
> firmly tied to the idea of blocks and disks and all that, making them less
> flexible than they should have been. That's why the Plan 9 version is about
> names and byte streams, to make it as general as possible.
> 
> That's one of the reasons the possibilities of the file system approach to
> data has not reached its potential in Unix.
> 
> -rob
> 
> 
> On Wed, Jun 24, 2020 at 1:14 AM Clem Cole <clemc at ccc.com> wrote:
> 
> > I agree with Larry with his observations.   The only thing I would add is
> > that Popek and Walker had a file system in the UCLA Locus distributed
> > system for the 11/70 that was published in SIGOPS in late 1970s.  In fact,
> > Gerry came up with the idea after a sabbatical @ PARC.   But it was not
> > formalized like NFS as a separate (layered) FS, it was just part of the
> > basic Locus FS.
> >
> > Peter Weinberger created the file system switch (FSS) for V8 and in the
> > UNIX world, it was first.    Dave Arnovitz used it for RFS in System V,
> > while Perry Flynn and I used it for EFS, both of us after talking
> > to Peter.   Rusty and team did the VFS layer Sun @ (Larry will have to tell
> > you who actually built it, I never knew).  Rusty and I both published
> > papers in the '85 Summer USENIX (NFS and EFS were contemporaries -- the
> > difference is that Sun gave away NFS and Masscomp was not smart enough to
> > do that).
> >
> > I talked to Steve Kleinman extensively about VFS at one point, and I'm
> > pretty sure he and the rest of the Sun guys had talked to the PARC folks
> > who after Gerry went back to UCLA started working on a DFS.   The idea of
> > the state-less (idempotent) file system RPC that NFS used based on stuff
> > PARC did.   But I'm not sure PARC had anything like the FSS or the VFS
> > layer.  Peter, Dave, and I used a stateful scheme because we chose to have
> > full UNIX FS semantics, which NFS did not.  In the end, early NFS was
> > notorious for putting 'holes' in the files because of the automatic seek in
> > every operation and errors not coming until close(2) time.
> >
> > EFS used an RPC and a RUDP layer that Perry and Alan Atlas built, but it
> > was not nearly as flexible as what Sun built [which had a crude interface
> > generator], although until years later when Mike Leibensger built PIG (the
> > Paceline Interface Generator) NFS RPC was always a PITA and not much better
> > in practice than what we had at Masscomp.
> >
> > In fact, the point of the EFS paper was it's all about the recovery when
> > there is a failure/error.  If you read his paper, Rusty's point was who
> > cares if there is an error (I've always felt vindicated that while I lost
> > the war, over time everyone came to our way of thinking and now NFS
> > V4 looks a whole lot like EFS did).
> >
> > Having a DFS as a feature was an incredible advance and proved we needed
> > something (and it needed to be standard in all systems).   NFS really lead
> > the market with that advance, although it sort of took a few years to make
> > it really good.  The fact is that others had the same idea before or at
> > least contemporary with it.
> >
> > That said, and to give the NFS team* a huge amount of credit *(and great
> > applause), the VFS layer was better thought out than the FSS and in fact
> > made it possible to add a lot of different file systems into UNIX later.
> > FSS was much more ad hoc.
> >
> > At LCC, when we built VPROC for TNC a few years later, we used some of the
> > same ideas from VFS and of course used VFS for the file system layer since
> > TNC had to have full POSIX semantics.  (It's a shame VPROC never caught on
> > the way VFS did).
> >
> > Clem
> >
> >
> > On Tue, Jun 23, 2020 at 10:02 AM Larry McVoy <lm at mcvoy.com> wrote:
> >
> >> I like to claim credit for creating the ChangeSet concept, the grouping
> >> of a set of deltas across a number of files.  But I wasn't the first.
> >> Back when dejanews was a thing and you could search usenet posts in a
> >> date range, if you searched before I started talking about ChangeSets,
> >> you could find 6, count 'em, 6 hits.  There was a really obscure system
> >> called Aide De Camp, that had a similar concept.
> >>
> >> But if you searched after I started talking about them you would see
> >> millions of hits.
> >>
> >> So I didn't invent the concept but I sure as heck made the world
> >> understand the concept.
> >>
> >> I suspect Sun could be in a similar position.  The VFS concept is
> >> pretty sweet so there might have been someone before Sun.  I'll
> >> long odds that if there was, it didn't gain traction until Sun
> >> did it.
> >>
> >> If there is nothing that predates it, then the inspiration was
> >> almost certainly the device driver interface.  One interface,
> >> many devices.  VFS is the same.
> >>
> >> On Tue, Jun 23, 2020 at 11:09:57AM +0200, Paul Ruizendaal wrote:
> >> > When googling for File System Switch or Virtual File System most
> >> sources mention Sun NFS and SysVr3 as the earliest implementations. Some
> >> sources mention 8th Edition.
> >> >
> >> > I did a (short) search  on FSS/VFS in earlier, non-Unix OS???s (Tenex,
> >> Multics, CTSS, etc.), but none of those seem to have had a comparable
> >> concept.
> >> >
> >> > Does anybody recall prior art (prior to 1984) in this area?
> >> >
> >> > Paul
> >>
> >> --
> >> ---
> >> Larry McVoy                  lm at mcvoy.com
> >> http://www.mcvoy.com/lm
> >>
> >

-- 
---
Larry McVoy            	     lm at mcvoy.com             http://www.mcvoy.com/lm 