[ClusterLabs] Antw: Re: Antw: [EXT] Re: Sub‑clusters / super‑clusters?

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Thu Aug 5 01:48:37 EDT 2021

>>> Antony Stone <Antony.Stone at ha.open.source.it> schrieb am 04.08.2021 um
21:27 in
Nachricht <202108042127.43916.Antony.Stone at ha.open.source.it>:
> On Wednesday 04 August 2021 at 20:57:49, Strahil Nikolov wrote:
>> That's why you need a qdisk at a 3‑rd location, so you will have 7 votes
>> total.When 3 nodes in cityA die, all resources will be started on the
>> remaining 3 nodes.
> I think I have not explained this properly.
> I have three nodes in city A which run resources which have to run in city 
> A.  
> They are based on IP addresses which are only valid on the network in city 
> A.
> I have three nodes in city B which run resources which have to run in city 
> B.  
> They are based on IP addresses which are only valid on the network in city 
> B.
> I have redundant routing between my upstream provider, and cities A and B, 
> so 
> that I only _need_ resources to be running in one of the two cities for 
> everything to work as required.  City A can go completely offline and not 
> run 
> its resources, and everything I need continues to work via city B.
> I now have an additional requirement to run a single resource at either city

> A 
> or city B but not both.
> As soon as I connect the clusters at city A and city B, and apply the 
> location 
> contraints and weighting rules you have suggested:
> 1. everything works, including the single resource at either city A or city

> B, 
> so long as both clusters are operational.
> 2. as soon as one cluster fails (all three of its nodes nodes become 
> unavailable), then the other cluster stops running all its resources as 
> well.  
> This is even with quorum=2.

Have you ever tried to find out why this happens? (Talking about logs)

> This means I have lost the redundancy between my two clusters, which is 
> based 
> on the expectation that only one cluster will fail at a time.  If the 
> failure 
> of one automatically _causes_ the failure of the other, I have no high 
> availability any more.
> What I require is for cluster A to continue running its own resources, plus

> the single resource which can run anywhere, in the event that cluster B 
> fails.
> In other words, I need the exact same outcome as I have at present if 
> cluster 
> B fails (its resources stop, cluster A is unaffected), except that cluster A

> continues to run the single resource which I need just a single instance
> It is impossible for the nodes at city A to run the resources which should 
> be 
> running at city B, partly because some of them are identical ("Asterisk" as

> a 
> resource, for example, is already running at city A), and partly because 
> some 
> of them are bound to the networking arrangements (I cannot set a floating IP

> address which belongs in city A on a machine which exists in city B ‑ it
> doesn't work).
> Therefore if adding a seventh node at a third location would try to start 
> _all_ resources in city A if city B goes down, it is not a working solution.

> If city B goes down then I simply do not want its resources to be running 
> anywhere, just the same as I have now with the two independent clusters.
> Thanks,
> Antony.
> ‑‑ 
> "In fact I wanted to be John Cleese and it took me some time to realise that

> the job was already taken."
>  ‑ Douglas Adams
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> me.
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