HA Cluster question

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dpu
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HA Cluster question

Post by dpu » 2017/12/22 04:31:15

I have a question regarding 2 node HA cluster configuration.

I am confused whether quorum configuration is required for 2 node cluster configuration on Cent OS 7. I was researching online and there were conflicting ideas. Somewhere its said it does not make sense to configure quorum disk on 2 node cluster, others highly recommend quorum disk configuration. Is it required?

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TrevorH
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Re: HA Cluster question

Post by TrevorH » 2017/12/22 10:12:56

No but fencing is required.
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dpu
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Re: HA Cluster question

Post by dpu » 2017/12/22 15:39:44

Thank You for your reply.

hunter86_bg
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Re: HA Cluster question

Post by hunter86_bg » 2017/12/22 19:48:18

You can consider using poison pill device (a.k.a. sbd) for fencing which can be provided over iscsi.For watchdog, you can use even 'softdog' kernel module.
In our production environment, we are using 3 sbd devices - one per each storage and one iscsi.

dpu
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Re: HA Cluster question

Post by dpu » 2017/12/23 23:10:54

Thank you for your reply. We are using vmware fencing agent.

dpu
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Re: HA Cluster question

Post by dpu » 2018/01/07 06:09:31

I configured fencing using the below command:

Code: Select all

# pcs stonith create sfence fence_vmware_soap ipaddr="vcenterIP" ipport=443 ssl=1 ssl_insecure=1 login='username' passwd='password' action=reboot pcmk_host_map="node1hostname:node1VMname;node2hostname:node2VMname"
However, sometimes the fencing resource does not start and I have to do a resource cleanup. Is it possible to configure a different fencing agent that will restart or poweroff virtualized (vmware) cluster nodes? I don't think vcenter user will be reliable as vcenter can be down!

Also, here is what I found on RHEL official docs regarding quorum device: A quorum device is recommended for clusters with an even number of nodes and highly recommended for two-node clusters.

hunter86_bg
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Re: HA Cluster question

Post by hunter86_bg » 2018/01/10 09:25:28

Another fencing mechanism is poison pill (a.k.a. sbd device).
You can load the 'softdog' module on both nodes. Prepare an iSCSI target that will host the sbd device and then login both nodes to this iSCSI target.
You can use up to 3 sbd devices and they are not limited only to iSCSI

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