Message-ID: <1322609431.11286.56.camel@lade.trondhjem.org>
Subject: Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes
From: Trond Myklebust <Trond.Myklebust@netapp.com>
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: Peng Tao <bergwolf@gmail.com>, linux-nfs@vger.kernel.org,
        bhalevy@tonian.com, Garth Gibson <garth@panasas.com>,
        Matt Benjamin <matt@linuxbox.com>, Marc Eshel <eshel@almaden.ibm.com>,
        Fred Isaman <iisaman@netapp.com>
Date: Tue, 29 Nov 2011 18:30:31 -0500
In-Reply-To: <4ED563AC.5040501@panasas.com>
References: <1322887965-2938-1-git-send-email-bergwolf@gmail.com>
	   <4ED54FE4.9050008@panasas.com> <4ED55399.4060707@panasas.com>
	  <1322603848.11286.7.camel@lade.trondhjem.org> <4ED55F78.205@panasas.com>
	 <1322606842.11286.33.camel@lade.trondhjem.org>
	 <4ED563AC.5040501@panasas.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Sender: linux-nfs-owner@vger.kernel.org

On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 02:47 PM, Trond Myklebust wrote:
> > On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
> >> On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> >>>> Also Files when they will support segments and servers that request segments,
> >>>> like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
> >>>> you know you want to write.
> >>>
> >>> Why would we want to add segment support to the pNFS files client???
> >>> Segments are a nuisance that multiply the amount of unnecessary chitchat
> >>> between the client and the MDS without providing any tangible
> >>> benefits...
> >>>
> >>
> >> Your kidding right?
> >>
> >> One: it is mandated by the Standard, This is not an option. So a perfectly
> >>      Standard complaint server is not Supported by Linux because we don't see
> >>      the point.
> > 
> > Bollocks.. Nothing is "mandated by the Standard". If the server doesn't
> > give us a full layout, then we fall back to write through MDS. Why dick
> > around with crap that SLOWS YOU DOWN.
> > 
> 
> NO! MAKE YOU FASTER.
> 
> The kind of typologies I'm talking about a single layout get ever 1GB is
> marginal to the gain I get in deploying 100 of DSs. I have thousands of
> DSs I want to spread the load evenly. I'm limited by the size of the layout
> (Device info in the case of files) So I'm limited by the number of DSs I can
> have in a layout. For large files these few devices become an hot spot all
> the while the rest of the cluster is idle.

I call "bullshit" on that whole argument...

You've done sod all so far to address the problem of a client managing
layout segments for a '1000 DS' case. Are you expecting that all pNFS
object servers out there are going to do that for you? How do I assume
that a generic pNFS files server is going to do the same? As far as I
know, the spec is completely moot on the whole subject.

IOW: I'm not even remotely interested in your "everyday problems" if
there are no "everyday solutions" that actually fit the generic can of
spec worms that the pNFS layout segments open.

> >> Two: There are already file-layout servers out there (multiple) which are
> >>      waiting for the Linux files-layout segment support, because the underline
> >>      FS requires Segments and now they do not work with the Linux client. These
> >>      are CEPH and GPFS and more.
> > 
> > Then they will have a _long_ wait....
> > 
> 
> OK, so now I understand. Because when I was talking to Fred before BAT and during
> It was very very peculiar to me why he is not already done with that simple stuff.
> Because usually Fred is such a brilliant fast programmer that I admire, and that simple
> crap?
> 
> But now that explains

Yes. It's all a big conspiracy, and we're deliberately holding Fred's
genius back in order to disappoint you...

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com