[Linux-cluster] Re: Question about Cluster Service

Robert Peterson rpeterso at redhat.com
Wed Feb 28 15:11:39 UTC 2007

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:

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

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.


Bob Peterson
Red Hat Cluster Suite

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