[ClusterLabs] stonith device locate on same host in active/passive cluster

[Ken Gaillot]

On 05/03/2017 09:04 PM, Albert Weng wrote:
> Hi Marek,
> 
> Thanks your reply.
> 
> On Tue, May 2, 2017 at 5:15 PM, Marek Grac <mgrac at redhat.com
> <mailto:mgrac at redhat.com>> wrote:
> 
> 
> 
>     On Tue, May 2, 2017 at 11:02 AM, Albert Weng <weng.albert at gmail.com
>     <mailto:weng.albert at gmail.com>> wrote:
> 
> 
>         Hi Marek,
> 
>         thanks for your quickly responding.
> 
>         According to you opinion, when i type "pcs status" then i saw
>         the following result of fence :
>         ipmi-fence-node1    (stonith:fence_ipmilan):    Started cluaterb
>         ipmi-fence-node2    (stonith:fence_ipmilan):    Started clusterb
> 
>         Does it means both ipmi stonith devices are working correctly?
>         (rest of resources can failover to another node correctly)
> 
> 
>     Yes, they are working correctly. 
> 
>     When it becomes important to run fence agents to kill the other
>     node. It will be executed from the other node, so the fact where
>     fence agent resides currently is not important
> 
> Does "started on node" means which node is controlling fence behavior?
> even all fence agents and resources "started on same node", the cluster
> fence behavior still work correctly?
>  
> 
> Thanks a lot.
> 
>     m,

Correct. Fencing is *executed* independently of where or even whether
fence devices are running. The node that is "running" a fence device
performs the recurring monitor on the device; that's the only real effect.

>         should i have to use location constraint to avoid stonith device
>         running on same node ?
>         # pcs constraint location ipmi-fence-node1 prefers clustera
>         # pcs constraint location ipmi-fence-node2 prefers clusterb
> 
>         thanks a lot

It's a good idea, so that a node isn't monitoring its own fence device,
but that's the only reason -- it doesn't affect whether or how the node
can be fenced. I would configure it as an anti-location, e.g.

   pcs constraint location ipmi-fence-node1 avoids node1=100

In a 2-node cluster, there's no real difference, but in a larger
cluster, it's the simplest config. I wouldn't use INFINITY (there's no
harm in a node monitoring its own fence device if it's the last node
standing), but I would use a score high enough to outweigh any stickiness.

>         On Tue, May 2, 2017 at 4:25 PM, Marek Grac <mgrac at redhat.com
>         <mailto:mgrac at redhat.com>> wrote:
> 
>             Hi,
> 
> 
> 
>             On Tue, May 2, 2017 at 3:39 AM, Albert Weng
>             <weng.albert at gmail.com <mailto:weng.albert at gmail.com>> wrote:
> 
>                 Hi All,
> 
>                 I have created active/passive pacemaker cluster on RHEL 7.
> 
>                 here is my environment:
>                 clustera : 192.168.11.1
>                 clusterb : 192.168.11.2
>                 clustera-ilo4 : 192.168.11.10
>                 clusterb-ilo4 : 192.168.11.11
> 
>                 both nodes are connected SAN storage for shared storage.
> 
>                 i used the following cmd to create my stonith devices on
>                 each node :
>                 # pcs -f stonith_cfg stonith create ipmi-fence-node1
>                 fence_ipmilan parms lanplus="ture"
>                 pcmk_host_list="clustera" pcmk_host_check="static-list"
>                 action="reboot" ipaddr="192.168.11.10"
>                 login=adminsitrator passwd=1234322 op monitor interval=60s
> 
>                 # pcs -f stonith_cfg stonith create ipmi-fence-node02
>                 fence_ipmilan parms lanplus="true"
>                 pcmk_host_list="clusterb" pcmk_host_check="static-list"
>                 action="reboot" ipaddr="192.168.11.11" login=USERID
>                 passwd=password op monitor interval=60s
> 
>                 # pcs status
>                 ipmi-fence-node1                     clustera
>                 ipmi-fence-node2                     clusterb
> 
>                 but when i failover to passive node, then i ran
>                 # pcs status
> 
>                 ipmi-fence-node1                    clusterb
>                 ipmi-fence-node2                    clusterb
> 
>                 why both fence device locate on the same node ? 
> 
> 
>             When node 'clustera' is down, is there any place where
>             ipmi-fence-node* can be executed?
> 
>             If you are worrying that node can not self-fence itself you
>             are right. But if 'clustera' will become available then
>             attempt to fence clusterb will work as expected.
> 
>             m, 
> 
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> 
> 
> 
>         -- 
>         Kind regards,
>         Albert Weng
> 
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