Messages in this thread | | | Date | Thu, 6 Dec 2001 11:11:27 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: SMP/cc Cluster description |
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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
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