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[Linux-cluster] restarting cluster from one node to multiple (Was: Re: rhel6 node start causes power on of the other one)



The pithy ruminations from "Fabio M. Di Nitto" <fdinitto redhat com> on "Re: [Linux-cluster] rhel6 node start causes power on of the other one" were:

=> Hi,
=> 
=> On 3/22/2011 11:12 AM, Gianluca Cecchi wrote:

	[SNIP!]

=> > 
=> > If the initial situation is both nodes down and I start one of them, I
=> > get it powering on the other, that is not my intentional target...

	[SNIP!]

=> 
=> This is expected behavior.
=> 

	[SNIP!]

=> I am not sure why you want a one node cluster, but one easy workaround

Sometimes, it's not a matter of "wanting" a one-node cluster, but being forced to have one temporarily. For example, if there's a hardware failure in one node of a 2-node cluster. I think that a likely scenario is that there's an event (for example, a power outage) that shuts down all nodes in a cluster, and that there is subsequent damage from that event (hardware failure, filesystem corruption on the local storage, etc.) that prevents some nodes from being restarted.

=> is to start both of them at the same time, and then shutdown one of

If both nodes are not available, this is not an easy work-around.

=> them. At that point they have both seen each other and the one going
=> down will tell the other "I am going offline, no worries, it´s all good".
=> 

What are the recommended alternative methods to starting a single-node on a cluster? If the number of expected votes is set to the number of votes for the single node, I'm able to start a single node. However, I'm not sure what will happen if additional nodes in the cluster are started later...will there be fencing or split-brain issues if "expected votes" is "1" when there are 2 nodes in the cluster?

Can additional nodes be brought up without affecting the services running on the existing node (ie., without causing the new node to fence the existing node)?

Thanks,

Mark


=> Fabio
=> 



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