[DRBD-user] 3-Node DRBD Without Stacking

Felix Frank ff at mpexnet.de
Tue Nov 16 18:45:03 CET 2010


On 11/16/2010 05:55 PM, Robinson, Eric wrote:
>>> Is it possible to deploy a 3-node CRM-based cluster where:
>>>
>>> 	-- nodes A and C share resource R1 on /dev/drbd0
>>>
>>> 	-- nodes B and C share resource R2 on /dev/drbd1
>>>
>>> 	-- resource constraints prevent R1 from running on node B and
> prevent 
>>> resource R2 from running on node A?
> 
>> I don't think I understand what you're trying to do. 
>> Please elaborate.
> 
>> Why would you need to prevent R1 from "running" on 
>> Host B if the resource is shared between A and C? 
>> B is not at all configured to connect to R1, is it?
> 
> It's a three-node CRM cluster where node C acts as a failover for nodes
> A and B, but nodes A and B do not fail over to each other. However, in a
> three-node CRM cluster, all resources are allowed to run on all nodes by
> default. For example, even though resource R1 only physically exists on
> nodes A and C, if node A fails Pacemaker might try to start it on node B
> if we don't put in some kind of constraints. You follow?  

I think I do now.

The ocf:linbit:drbd RA should be smart enough to realize that R1 is not
configured (in drbd.conf) to ever run on R1. But don't quote me on that.

If you are still afraid it might take a nonsensical action and bring a
DRBD device up on a node that is not configured to do that, feel free to
add a constraint like

location p_drbd_r1_not_on_hostB -inf: p_drbd_r1 hostB

or something along those lines.

HTH,
Felix


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