[ClusterLabs] [EXT] Re: Two node cluster without fencing and no split brain?
Ulrich.Windl at rz.uni-regensburg.de
Wed Jul 21 08:55:45 EDT 2021
Maybe someone feels motivated to write some article comparing the concepts
* split brain
There are eight possible states that I tried to illustrate on the attached sketch (S="Split Brain", "Q=Quorum, F=Fencing).
>>> Andrei Borzenkov 21.07.2021, 07:52 >>>
On 21.07.2021 07:28, Strahil Nikolov via Users wrote:
> consider using a 3rd system as a Q disk.
What was not clear in "Quorum is a different concept and doesn't remove
the need for fencing"?
> Also, you can use iscsi from that node as a SBD device, so you will have proper fencing .If you don't have a hardware watchdog device, you can use softdog kernel module for that.
> Best Regards,Strahil Nikolov
> On Wed, Jul 21, 2021 at 1:45, Digimer<lists at alteeve.ca> wrote: On 2021-07-20 6:04 p.m., john tillman wrote:
>> Is it possible to configure a two node cluster (pacemaker 2.0) without
>> fencing and avoid split brain?
>> I was hoping there was a way to use a 3rd node's ip address, like from a
>> network switch, as a tie breaker to provide quorum. A simple successful
>> ping would do it.
> Quorum is a different concept and doesn't remove the need for fencing.
>> I realize that this 'ping' approach is not the bullet proof solution that
>> fencing would provide. However, it may be an improvement over two nodes
> It would be, at best, a false sense of security.
>> Is there a configuration like that already? Any other ideas?
>> Pointers to useful documents/discussions on avoiding split brain with two
>> node clusters would be welcome.
> (note: currently throwing a cert error related to the let's encrypt
> issue, should be cleared up soon).
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