Re: 3 or 4 nodes in a RAC?


As far as n-way communications are concerned it doesn't get worse than 3.
Node A (who wants a particular resource) asks Node B (who is the master for the resource) to tell Node C (who is currently exclusive owner of the resource) to pass it to Node A 

It doesn't matter how many nodes there are, the loop is always a triangle.

On the other hand, the fewer nodes you have the more likely you are to be the
master of a particular resource (no N-way negotiation), and the more likely that the master also happens to be the owner if you aren't the master (better 
chance of 2-way rather than 3 way).



Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com
----- Original Message ----- From: "Guillermo Alan Bort" <cicciuxdba@xxxxxxxxx> 
To: "oracle-l-freelists" <oracle-l@xxxxxxxxxxxxx>
Sent: Thursday, June 09, 2011 3:51 PM
Subject: 3 or 4 nodes in a RAC?



List

 This is a design question.... We are building a new RAC, we currently have
a 4 node RAC and we are upgrading the hardware and software and are
wondering whether to go with a 3 node RAC or a 4 node RAC. I've heard rumors
that 3node RAC perform better (we have no 4-way current gc waits, but there
are a lot of 3-way current waits)...

  So, what I'm looking for is links or experiences regarding 3-way and
4-way RACs.

Thanks in advance

Alan.-



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