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Re: [Linux-cluster] Re: Question about Cluster Service



sara sodagar wrote:
Hi
Thank you very much for replying to my question.
My first problem is whether I can use one node (Node
C)
as a passive for two separate cluster
service(service1,service2).
We are using SAN in our solution and I think there is
no need for Node C to have a copy of the data on A ,
because
it's a waste of storage on SAN.It should have an
access
on data on A in case of failure.(I don't know if this
is necessary to have GFS between A,C or not?)

--Regards.
Sara
Hi Sara,

I am still confused by your explanation, but I'll try to answer your
question anyway.

Yes, it's possible for C to be a passive (failover) server for node
both A and B.  I'm not an rgmanager expert, but I think you can do
this by configuring two failover domains in your /etc/cluster/cluster.conf.
I don't know what service you need to fail over to "C" but here's an
example that uses a virtual IP address service:

              <failoverdomains>
<failoverdomain name="igridnodes1" ordered="1" restricted="1">
                              <failoverdomainnode name="A" priority="1"/>
                              <failoverdomainnode name="C" priority="2"/>
                      </failoverdomain>
<failoverdomain name="igridnodes2" ordered="1" restricted="1">
                              <failoverdomainnode name="B" priority="1"/>
                              <failoverdomainnode name="C" priority="2"/>
                      </failoverdomain>
               </failoverdomains>
               <resources>
                       <ip address="10.0.0.1" monitor_link="1"/>
                       <ip address="10.0.0.2" monitor_link="1"/>
               </resources>
               <service autostart="1" domain="igridnodes1" name="10.0.0.1">
                       <ip ref="10.0.0.1"/>
               </service>
               <service autostart="1" domain="igridnodes2" name="10.0.0.2">
                       <ip ref="10.0.0.2"/>
               </service>

This basically defines two virtual IP addresses, one for "A" but "C" can take over
if A fails, and a second one for "B" but "C" can take over if B fails.
They are ordered, which means prioritized, and "A" is given highest priority
for one, and "B" for the other.  That means A and B should be running the
service until they fail.  If they fail, C will be used to host the service.
In this example, the services are virtual IP addresses, but you can use this
same basic idea to define any service; even your own custom service if you want.

Unless I misunderstood your description, it sounds like your data is kept
on a SAN, and you want "C" to be able to serve the same data on that SAN
(not a copy) for both "A" and "B". If that's the case, then the storage is shared
between A and C, and yes, you want to use GFS to manage the data.
I hope this answers your question.

Regards,

Bob Peterson
Red Hat Cluster Suite


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