[ClusterLabs] Antw: Re: [EXT] Re: Two node cluster without fencing and no split brain?

[Strahil Nikolov]

So far, I never had a cluster with nodes directly connected to the same switches. Usually it's a nodeA -> switchA -> switchB -> nodeB and sometimes connectivity between switches goes down (for example a firewall rule).

Best Regards,
Strahil Nikolov






В сряда, 28 юли 2021 г., 15:51:36 ч. Гринуич+3, john tillman <johnt at panix.com> написа: 







> Technically you could give one vote to one node and zero to the other. 
> If they lose contact only the server with one vote would make quorum. 
> The downside is that if the server with 1 vote goes down the entire
> cluster comes to a halt.
>
>
> That said, if both nodes can reach the same switch that they are
> connected to each other through, why can't they reach each other?
>

"... why can't they reach each other?"  My question as well.

It feels like a very low probability thing to me.  Some
blockage/filtering/delay of the cluster's "quorum packets" while ping
packets were allowed through, perhaps caused by network congestion.  But
I'm not a network engineer.  Any network engineers reading this care to
comment?

Thanks for echoing my thoughts and that interesting quorum-weight idea.


>
> On 7/26/21 12:21 PM, john tillman wrote:
>> They would continue running their resources and we would have split
>> brain.
>>
>> So there is no safe way to support a two node cluster 100% of the time.
>> But when all you have are two nodes and a switch ... well, when life
>> gives
>> you lemons ...
>
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