[ClusterLabs] Antw: [EXT] Re: qnetd and booth arbitrator running together in a 3rd geo site

[Ulrich Windl]

>>> Rohit Saini <rohitsaini111.forum at gmail.com> schrieb am 14.07.2020 um 13:52 in
Nachricht
<CA+ZsWTVjS+EUtmp4KRww023PrQkB+hGvi9WB-7+A2E0stumrNQ at mail.gmail.com>:
> Thanks Honza. I guess qnetd+booth will be best in my case as you also
> suggested.

Actually I just wonder if "best" still does prevent data corruption.
There are many creative ways for data corruption. Some years ago we had a nicely corrupted RPM database when a node was fenced while some package installation was in progress...
Another time the cluster mounted a filesystem that would have needed repair first.... (Yes, in theory journaled filesystems don't need "repair")

> 
> Regards,
> Rohit
> 
> On Tue, Jul 14, 2020 at 5:19 PM Jan Friesse <jfriesse at redhat.com> wrote:
> 
>> 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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>> >>>>
>> >>>
>> >>
>> >>
>> >
>>
>>