Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id <S282640AbRLFTBw>; Thu, 6 Dec 2001 14:01:52 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org
	id <S282547AbRLFTBf>; Thu, 6 Dec 2001 14:01:35 -0500
Received: from mail.xmailserver.org ([208.129.208.52]:48646 "EHLO
	mail.xmailserver.org") by vger.kernel.org with ESMTP
	id <S282502AbRLFTA1>; Thu, 6 Dec 2001 14:00:27 -0500
Date: Thu, 6 Dec 2001 11:11:27 -0800 (PST)
From: Davide Libenzi <davidel@xmailserver.org>
X-X-Sender: davide@blue1.dev.mcafeelabs.com
To: "Jeff V. Merkey" <jmerkey@vger.timpanogas.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
In-Reply-To: <20011206112731.C22534@vger.timpanogas.org>
Message-ID: <Pine.LNX.4.40.0112061046110.1603-100000@blue1.dev.mcafeelabs.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

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.




- Davide




-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/