Oracle's RAC is good, but I think it's best to view it as a step in the high availability direction rather than a performance enhancer. While it can help your application scale up, that depends on the usage pattern. Also it's not 100% transparent to the application for example you can't depend on a sequence numbers being allocated uniquely as there can be delays propagating them to all nodes. So in clusters where insert rates are high this means you should explicitly check for unique key violations and try again. Dealing with propagation delays comes with the clustering technology I guess. Nonetheless, I would love to see this kind of functionality in postgres.


----- Original Message ----- From: "Jim C. Nasby" <[EMAIL PROTECTED]>
To: "Bruno Almeida do Lago" <[EMAIL PROTECTED]>
Cc: "'Mitch Pirtle'" <[EMAIL PROTECTED]>; <>
Sent: Friday, January 21, 2005 10:30 AM
Subject: Re: [PERFORM] PostgreSQL clustering VS MySQL clustering

On Thu, Jan 20, 2005 at 10:40:02PM -0200, Bruno Almeida do Lago wrote:

I was thinking the same! I'd like to know how other databases such as Oracle
do it.

In a nutshell, in a clustered environment (which iirc in oracle means
shared disks), they use a set of files for locking and consistency
across machines. So you better have fast access to the drive array, and
the array better have caching of some kind.
Jim C. Nasby, Database Consultant               [EMAIL PROTECTED]
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