[ClusterLabs] qnetd and booth arbitrator running together in a 3rd geo site

[Jan Friesse]

Rohit,

> I dont think my question was very clear. I am strictly NO for STONITH.
> STONITH is limited only for kvm or HP machines. That's the reason I don't

Nope, stonith is not limited only for KVM or HP machine. There is huge 
amount of fence agents for various HW and VMs 
(https://github.com/ClusterLabs/fence-agents/tree/master/agents). Also 
there is SBD.


> want to use STONITH.
> What my question is can I use booth with nodes of a single cluster also
> (similar to qdevice)? So idea is to use booth arbitrator for cluster of

Standard way to use booth is to have 2 clusters with N nodes. On each 
cluster, there is clustered booth, which is running in active-passive 
fashion (so only on one of the nodes of the cluster). And this booth 
gives ticket depending on booth arbitrator decision. And final piece of 
puzzle is pacemaker resource which depends on ownership of ticket.


> clusters AS WELL AS for a single cluster.

So something like a booth resource in one cluster depending on booth 
ticket given by some locally running booth? I would say in theory it is 
possible, but I would say original idea of using both qnetd and booth 
looked a bit more "standard".

Honza

> 
> 
> On Tue, Jul 14, 2020 at 4:42 PM Jan Friesse <jfriesse at redhat.com> wrote:
> 
>> Rohit,
>>
>>> Thanks Honja. That's helpful.
>>> Let's say I don't use qnetd, can I achieve same with booth arbitrator?
>>
>> That means to have two two-node clusters. Two-node cluster without
>> fencing is strictly no.
>>
>>> Booth arbitrator works for geo-clusters, can the same arbitrator be
>> reused
>>> for local clusters as well?
>>
>> I'm not sure that I understand question. Booth just gives ticket to
>> (maximally) one of booth-sites.
>>
>>
>>> Is it even possible technically?
>>
>> The question is, what you are trying to achieve. If geo-cluster then
>> stonith for sites + booth is probably best solution. If the cluster is
>> more like a stretch cluster, then qnetd + stonith is enough.
>>
>> And of course your idea (original one) should work too.
>>
>> Honza
>>
>>
>>>
>>> Regards,
>>> Rohit
>>>
>>> On Tue, Jul 14, 2020 at 3:32 PM Jan Friesse <jfriesse at redhat.com> wrote:
>>>
>>>> Rohit,
>>>>
>>>>> Hi Team,
>>>>> Can I execute corosync-qnetd and booth-arbitrator on the same VM in a
>>>>> different geo site? What's the recommendation? Will it have any
>>>> limitations
>>>>> in a production deployment?
>>>>
>>>> There is no technical limitation. Both qnetd and booth are very
>>>> lightweight and work just fine with high latency links.
>>>>
>>>> But I don't really have any real-life experiences with deployment where
>>>> both booth and qnetd are used. It should work, but I would recommend
>>>> proper testing - especially what happens when arbitrator node
>> disappears.
>>>>
>>>>> Due to my architecture limitation, I have only one arbitrator available
>>>>> which is on a 3rd site. To handle cluster split-brain errors, I am
>>>> thinking
>>>>> to use same arbitrator for local cluster as well.
>>>>> STONITH is not useful in my case as it is limited only to ILO and VIRT.
>>>>
>>>> Keep in mind that neither qdevice nor booth is "replacement" for
>> stonith.
>>>>
>>>> Regards,
>>>>      Honza
>>>>
>>>>>
>>>>> [image: image.png]
>>>>>
>>>>> Thanks,
>>>>> Rohit
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>
>>
>>
>