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 

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_at_gmail.com> To: "oracle-l-freelists" <oracle-l_at_freelists.org> 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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