[Pacemaker] Different Corosync Rings for Different Nodes in Same Cluster?

[Steven Dake]

On 06/29/2012 01:42 AM, Dan Frincu wrote:
> Hi,
> 
> On Thu, Jun 28, 2012 at 6:13 PM, Andrew Martin <amartin at xes-inc.com> wrote:
>> Hi Dan,
>>
>> Thanks for the help. If I configure the network as I described - ring 0 as
>> the network all 3 nodes are on, ring 1 as the network only 2 of the nodes
>> are on, and using "passive" - and the ring 0 network goes down, corosync
>> will start using ring 1. Does this mean that the quorum node will appear to
>> be offline to the cluster? Will the cluster attempt to STONITH it? Once the
>> ring 0 network is available again, will corosync transition back to using it
>> as the communication ring, or will it continue to use ring 1 until it fails?
>>
>> The ideal behavior would be when ring 0 fails it then communicates over ring
>> 1, but keeps periodically checking to see if ring 0 is working again. Once
>> it is, it returns to using ring 0. Is this possible?
> 
> Added corosync ML in CC as I think this is better asked here as well.
> 
> Regards,
> Dan
> 
>>
>> Thanks,
>>
>> Andrew
>>
>> ________________________________
>> From: "Dan Frincu" <df.cluster at gmail.com>
>> To: "The Pacemaker cluster resource manager" <pacemaker at oss.clusterlabs.org>
>> Sent: Wednesday, June 27, 2012 3:42:42 AM
>> Subject: Re: [Pacemaker] Different Corosync Rings for Different Nodes
>> in        Same Cluster?
>>
>>
>> Hi,
>>
>> On Tue, Jun 26, 2012 at 9:53 PM, Andrew Martin <amartin at xes-inc.com> wrote:
>>> Hello,
>>>
>>> I am setting up a 3 node cluster with Corosync + Pacemaker on Ubuntu 12.04
>>> server. Two of the nodes are "real" nodes, while the 3rd is in standby
>>> mode
>>> as a quorum node. The two "real" nodes each have two NICs, one that is
>>> connected to a shared LAN and the other that is directly connected between
>>> the two nodes (for DRBD replication). The quorum node is only connected to
>>> the shared LAN. I would like to have multiple Corosync rings for
>>> redundancy,
>>> however I do not know if this would cause problems for the quorum node. Is
>>> it possible for me to configure the shared LAN as ring 0 (which all 3
>>> nodes
>>> are connected to) and set the rrp_mode to passive so that it will use ring
>>> 0
>>> unless there is a failure, but to also configure the direct link between
>>> the
>>> two "real" nodes as ring 1?
>>

In general I think you cannot do what you describe.  Let me repeat it so
its clear:

A B C - NET #1
A B   - Net #2

Where A, B are your cluster nodes, and C is your quorum node.

You want Net #1 and Net #2 to serve as redundant rings.  Since C is
missing, Net #2 will automatically be detected as faulty.

The part about corosync automatically repairing nodes is correct, that
would work (If you had a complete network).

Regards
-steve

>> Short answer, yes.
>>
>> Longer answer. I have a setup with two nodes with two interfaces, one
>> is connected via a switch to the other node and one is a back-to-back
>> link for DRBD replication. In Corosync I have two rings, one that goes
>> via the switch and one via the back-to-back link (rrp_mode: active).
>> With rrp_mode: passive it should work the way you mentioned.
>>
>> HTH,
>> Dan
>>
>>>
>>> Thanks,
>>>
>>> Andrew
>>>
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>>>
>>
>>
>>
>> --
>> Dan Frincu
>> CCNA, RHCE
>>
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>>
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>>
>>
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>>
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>>
> 
> 
>