[ClusterLabs] Question about ping nodes

[Antony Stone]

On Saturday 17 April 2021 at 21:41:16, Piotr Kandziora wrote:

> Hi,
> 
> Hope some guru will advise here ;)
> 
> I've got two nodes cluster with some resource placement dependent on ping
> node visibility (
> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/ht
> ml/high_availability_add-on_reference/s1-moving_resources_due_to_connectivi
> ty_changes-haar ).
> 
> Is it possible to do nothing with these resources when both nodes do not
> have access to the ping node?

The whole purpose of a ping node is to give a resource node confidence that it 
can safely provide resources to the network.  If it loses connectivity to the 
ping node, it considers itself dead / offline / non-functional.

If both resource nodes lose contact with the ping node, then neither of them 
have the confidence to provide resources, so both of them stop doing so.

All I can say is that if this is possible then either your resource nodes have 
poor network connectivity and should not be used as resource nodes, or else 
the ping node has poor reachability and should not be used as a ping node.

> Currently, when the ping node is unavailable (node itself becomes
> unavailable) both nodes stop the resources.

This is correct.  Neither node can tell whether it should take charge of the 
resources, so for the sake of safety, they both decline to do so.

Two node clusters are intrinsically fragile in this respect.


Antony.

-- 
https://tools.ietf.org/html/rfc6890 - providing 16 million IPv4 addresses for 
talking to yourself.

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