[ClusterLabs] DRBD on asymmetric-cluster

[Jason Voorhees]

I started reading "Pacemaker explained" but as it's so depth I didn't
read that section regarding rules yet. I'll take a look at it and test
it before asking anything again.

Thanks a lot Ken

On Mon, Apr 4, 2016 at 9:26 AM, Ken Gaillot <kgaillot at redhat.com> wrote:
> On 04/02/2016 01:16 AM, Jason Voorhees wrote:
>> Hello guys:
>>
>> I've been recently reading "Pacemaker - Clusters from scratch" and
>> working on a CentOS 7 system with pacemaker 1.1.13, corosync-2.3.4 and
>> drbd84-utils-8.9.5.
>>
>> The PDF instructs how to create a DRBD resource that seems to be
>> automatically started due to a symmetric-cluster setup.
>>
>> However I want to setup an asymmetric-cluster/opt-in
>> (symmetric-cluster=false) but I don't know how to configure a
>> constraint to prefer node1 over node2 to start my DRBD resource as
>> Master (Primary).
>
> I thought location constraints supported role, but that isn't
> documented, so I'm not sure. But it is documented with regard to rules,
> which using pcs might look like:
>
> pcs location clusterdataClone rule \
>   role=master \
>   score=50 \
>   '#uname' eq nodo1
>
> For a lower-level explanation of rules, see
> http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Explained/index.html#idm140617356537136
>
>> So far this are my resources and constraints:
>>
>> [root at nodo1 ~]# pcs resource
>>  IPService      (ocf::heartbeat:IPaddr2):       Started nodo1
>>  Web    (systemd:httpd):        Started nodo1
>>  Master/Slave Set: clusterdataClone [clusterdata]
>>      Stopped: [ nodo1 nodo2 ]
>>
>> [root at nodo1 ~]# pcs constraint
>> Location Constraints:
>>   Resource: IPService
>>     Enabled on: nodo2 (score:50)
>>     Enabled on: nodo1 (score:100)
>>   Resource: Web
>>     Enabled on: nodo2 (score:50)
>>     Enabled on: nodo1 (score:100)
>> Ordering Constraints:
>>   start IPService then start Web (kind:Mandatory)
>> Colocation Constraints:
>>   Web with IPService (score:INFINITY)
>>
>> My current DRBD status:
>>
>> [root at nodo1 ~]# drbdadm role clusterdb
>> 0: Failure: (127) Device minor not allocated
>> additional info from kernel:
>> unknown minor
>> Command 'drbdsetup-84 role 0' terminated with exit code 10
>>
>>
>> [root at nodo2 ~]# drbdadm role clusterdb
>> 0: Failure: (127) Device minor not allocated
>> additional info from kernel:
>> unknown minor
>> Command 'drbdsetup-84 role 0' terminated with exit code 10
>>
>>
>> I know that it's possible to configure my cluster as asymmetric and
>> use constraints to avoid a resource running (or becoming master) on
>> certain nodes, but this time I would like to learn how to do it with
>> an opt-in scenario.
>>
>> Thanks in advance for your help.
>>
>> P.D. nodo1 & nodo2 are spanish names for node1 and node2
>>
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>
>
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