Subject: Re: Proxy
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: maillists0@gmail.com
Cc: "J. Bruce Fields" <bfields@fieldses.org>, linux-nfs@vger.kernel.org
In-Reply-To: <t2ndc64e7231005031414ob1ca0ebaze725bb73e712234d@mail.gmail.com>
References: <l2wdc64e7231005030953xb72ad73az3f883167a1a637c8@mail.gmail.com>
	 <20100503185650.GA9864@fieldses.org>
	 <1272914702.7559.13.camel@localhost.localdomain>
	 <t2ndc64e7231005031414ob1ca0ebaze725bb73e712234d@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Date: Mon, 03 May 2010 18:16:13 -0400
Message-ID: <1272924973.7559.19.camel@localhost.localdomain>
Sender: linux-nfs-owner@vger.kernel.org
MIME-Version: 1.0

On Mon, 2010-05-03 at 17:14 -0400, maillists0@gmail.com wrote: 
> On Mon, May 3, 2010 at 3:25 PM, Trond Myklebust
> <trond.myklebust@fys.uio.no> wrote:
> > On Mon, 2010-05-03 at 14:56 -0400, J. Bruce Fields wrote:
> >> On Mon, May 03, 2010 at 12:53:15PM -0400, maillists0@gmail.com wrote:
> >> > With NFS4's support for referrals and Kerberos, it seems like the
> >> > original reasons to prevent re-exporting of an NFS share might no
> >> > longer exist. With fs-proxy making its way into the mainline kernel
> >> > and things like cachefilesd, there are also very good reasons to allow
> >> > it. A proxy server with a persistent cache could give the ability to
> >> > robustly use shares across a WAN or do failover pairs with no need for
> >> > more complex replication. Speaking as an end-user, this would be very
> >> > desirable.
> >> >
> >> > I see that others have implemented proxies with user-space NFS, which
> >> > seems reasonable but not optimal. What is the obstacle to allowing
> >> > re-exports with the standard nfs implentation? Is it possible at the
> >> > moment to patch a kernel to make this work? Anyone have experience
> >> > with it? Any input is appreciated.
> >>
> >> It's probably possible, but some kernel hacking would be required.
> >>
> 
> Have a look at this old thing from 2006:
> http://www.usenix.org/event/fast07/tech/full_papers/gulati/gulati_html/nache.html
> . They claim to have implemented a proxy with only the tools I
> mentioned above, along with their own modified version of nfs to allow
> multi-hops.
> 
> I have a workload of lots of reads/almost no writes, and their
> approach makes sense. It would be a great feature. Is something
> missing from that paper that makes it unrealistic?

Possibly not for your workload, but none of the issues Bruce and I
raised appear to be addressed in that paper.

Furthermore, we do know several of the authors, and none of them have
ever approached us with a proposal to merge their implementation. I
therefore assume that it was written more as a proof of concept in
support of the paper, rather than something IBM is actually planning to
market.

Cheers
  Trond