RE: RAC newbie question

From: Yavor Ivanov <>
Date: Tue, 7 Oct 2008 09:26:20 +0300
Message-ID: <BD17E2E69E17C64A9684C940EB580E03010D7D55B1D3@stemodc1.stemo.local>

        Usualy I would go with single 9-node cluster too. Same reasons. But there are some more things to consider here.

        Think about cluster upgrades. If you have one cluster to upgrade, this sounds like single downtime window. But what if one database needs a newer version (and newer clusterware), and the other cannot afford downtime at that moment? This is something rare, but it's not bad to think of it.

        Also, some influences may come from your backup / DR strategy. But this goes too deep, and gives too little value.

        But as I've said, I'd usually go to 9-node with every app running on different nodes.

Yavor Ivanov
Oracle Certified Master

-----Original Message-----
From: [] On Behalf Of Dan Norris Sent: Monday, October 06, 2008 9:47 PM
Cc: Mercadante, Thomas F (LABOR); Subject: Re: RAC newbie question


I would absolutely create these 9 servers in a single cluster, but that doesn't necessarily mean that each database has an instance on each node. You can (and I would) build a 9-node cluster, but have database instances running on nodes 1-2, a different database on node 3-7, and a third database running on nodes 8-9. This would/should allow you to bring up an instance for database #1 on another node if node 2 were to fail. If they are separate clusters, that would not be possible.

This is along the lines of what Oracle's Grid architecture intends to promote. I would not advocate running all instances on all nodes when you have enough nodes to avoid such a case. Oracle's resource management is only within a single instance (at least in currently-available releases), so two instances on the same node can and will have potential to suck up all resources on the node without regard to the other instance(s) on that node.

The other questions that Tom M. asked are good ones and should be part of your consideration as well. In general, even before I knew the answers you gave, I'd advocate an architecture similar to what I've described above.


Terrian, Thomas J Mr CTR DLA J6DIB wrote:
> Are these three production databases? YES
> Any development or staging to worry about? YES, they are on other
> machines on one cluster.
> Does any individual database have a higher profile than the others? Not
> sure what you are asking.
> Does it need to be alone for political/business reasons? Good question,
> right now each program manager wants his own cluster. We are looking to
> see if it may be better for the organization to just set up one
> production cluster.
> Do any of these databases hold a warehouse? Are any a reporting only
> database? NO, OLTP.


Received on Tue Oct 07 2008 - 01:26:20 CDT

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