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Re: [Linux-cluster] Is this possible?



On Mon, 2006-12-04 at 20:28 +0200, Eftychios Eftychiou wrote:

> Is it possible for CMAN to make it start the same application on for
> example 2 nodes and have as a failover a third or more nodes? 

Well, cman doesn't really do that, but yes...

Something like this:
 
 <failoverdomains>
   <failoverdomain name="nodes13" ordered="1">
     <failoverdomainnode name"node1" priority="1"/>
     <failoverdomainnode name"node3" priority="2"/>
   </failoverdomain>
   <failoverdomain name="nodes23" ordered="1">
     <failoverdomainnode name"node2" priority="1"/>
     <failoverdomainnode name"node3" priority="2"/>
   </failoverdomain>
 </failoverdomain>  

 <resources>
   <script name="foo" file="/tmp/foo-script"/>
 </resources>

 <service name="svc1" domain="nodes13">
   <script ref="foo"/>
 </service>
 <service name="svc2" domain="nodes23">
   <script ref="foo"/>
 </service>

svc1 starts on node 1, unless node 1 isn't online, then it starts on 3.
svc2 starts on node 2, unless node 2 isn't online, then it starts on 3.

This works because while "services" may only be started on a single
node, certain resources such as a script may be shared between more than
one service.

(Assuming you don't do any tricks, only one node in the cluster would
cause a loss of quorum, so services wouldn't run at all.)

It's two services, but they're starting the same application.  (Note:
You can not, however, reference the same ext3 file system or IP address
twice.)

-- Lon

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