On Thu, Dec 06, 2001 at 03:16:13PM -0800, David Lang wrote:
> also some applications (i.e. databases) are such that nobody has really
> been able to rewrite them into the shared nothing model (although oracle
> has attempted it, from what I hear it has problems)
> 
> David Lang

OPS (Oracle Parallel Server) is shared nothing.  

Jeff


> 
>  On Thu, 6 Dec 2001,
> Jeff V. Merkey wrote:
> 
> > Date: Thu, 6 Dec 2001 12:34:48 -0700
> > From: Jeff V. Merkey <jmerkey@vger.timpanogas.org>
> > To: Davide Libenzi <davidel@xmailserver.org>
> > Cc: David S. Miller <davem@redhat.com>, lm@bitmover.com,
> >      rusty@rustcorp.com.au, Martin J. Bligh <Martin.Bligh@us.ibm.com>,
> >      Rik vav Riel <riel@conectiva.com.br>, lars.spam@nocrew.org,
> >      Alan Cox <alan@lxorguk.ukuu.org.uk>, hps@intermeta.de,
> >      lkml <linux-kernel@vger.kernel.org>, jmerkey@timpanogas.org
> > Subject: Re: SMP/cc Cluster description
> >
> > On Thu, Dec 06, 2001 at 11:11:27AM -0800, Davide Libenzi wrote:
> > > On Thu, 6 Dec 2001, Jeff V. Merkey wrote:
> > >
> > > > Guys,
> > > >
> > > > I am the maintaner of SCI, the ccNUMA technology standard.  I know
> > > > alot about this stuff, and have been involved with SCI since
> > > > 1994.  I work with it every day and the Dolphin guys on some huge
> > > > supercomputer accounts, like Los Alamos and Sandia Labs in NM.
> > > > I will tell you this from what I know.
> > > >
> > > > A shared everything approach is a programmers dream come true,
> > > > but you can forget getting reasonable fault tolerance with it.  The
> > > > shared memory zealots want everyone to believe ccNUMA is better
> > > > than sex, but it does not scale when compared to Shared-Nothing
> > > > programming models.  There's also a lot of tough issues for dealing
> > > > with failed nodes, and how you recover when peoples memory is
> > > > all over the place across a nuch of machines.
> > >
> > > If you can afford rewriting/rearchitecting your application it's pretty
> > > clear that the share-nothing model is the winner one.
> > > But if you can rewrite your application using a share-nothing model you
> > > don't need any fancy clustering architectures since beowulf like cluster
> > > would work for you and they'll give you a great scalability over the
> > > number of nodes.
> > > The problem arises when you've to choose between a new architecture
> > > ( share nothing ) using conventional clusters and a
> > > share-all/keep-all-your-application-as-is one.
> > > The share nothing is cheap and gives you a very nice scalability, these
> > > are the two mayor pros for this solution.
> > > On the other side you've a vary bad scalability and a very expensive
> > > solution.
> > > But you've to consider :
> > >
> > > 1) rewriting is risky
> > >
> > > 2) good developers to rewrite your stuff are expensive ( $100K up to $150K
> > > 	in my area )
> > >
> > > These are the reason that let me think that conventional SMP machines will
> > > have a future in addition to my believing that technology will help a lot
> > > to improve scalability.
> > >
> >
> > There's a way through the fog.  Shared Nothing with explicit coherence.
> > You are correct, applications need to be rewritten to exploit it.  It
> > is possible to run existing SMP apps process -> process across nodes
> > with ccNUMA, and this works, but you don't get the scaling as shared
> > nothing.
> >
> > Jeff
> >
> > Jeff
> >
> >
> > >
> > >
> > >
> > > - Davide
> > >
> > >
> > >
> > -
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> >
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