[DRBD-user] Dual-Primary Split Brain

raveenpl raveenpl at gmail.com
Thu Sep 30 22:54:35 CEST 2010

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Thanks for answer and your proposition.

But I am rather intersted in how it should behave in such situation. I know
that with DRBD I have to way to cope with Split-Brain: manual and automatic
(and automatic way highly depend on your solution).

Let's assume that I would like use only manual way for recovering after
split brain (this is what did you say - I should choose more up to date node
and synchronize data with it). It is ok for me. But are there any good
practices in case of disconnecting two primary nodes? I mean for example:
killing node, switching node to read-only mode and so on? I would like to
know how it should be behave in case of disconnecting nodes.


Digimer wrote:
> On 10-09-30 10:39 AM, raveenpl wrote:
>> Hello,
>> I would like to have Primary/Primary cluster. The most wondering in this
>> solution is for me how to cope with split-brain sitaution. 
>> I know that they are to two ways to fence nodes (on resource level and
>> using
>> STONITH) - but how they work in dual-primary mode? Maybe somebody could
>> give
>> step-by-step example?
>> Cheers
>> RaveenPL
> I use it with Red Hat Cluster Services and their fence daemon. I've got
> an in-progress How-To, but it's not finished enough to post publicly
> here. If you're okay with that, and are interested, send me an email
> off-list and I'll send you the link.
> The setup is:
> - RAID Level 1 on either node.
> - Cluster built using RHCS Cluster Stable 3 on Fedora 13 (until RHEL 6
> is released).
> - DRBD across the two nodes.
> - CLVM on top of the DRBD resource.
> If your question is more to do with recovering from split brain, then
> it's as follows. Note that in this case, I chose 'Node 1' to be the most
> up to date node. You'll need to make that decision yourself in the real
> world.
> -= Node 1		-= Node2
> modprobe drbd		modprobe drbd
> drbdadm attach r0	drbdadm attach r0
> 			drbdadm invalidate r0
> drbdadm connect r0	drbdadm connect r0
> drbdadm primary r0	drbdadm primary r0
> -- 
> Digimer
> E-Mail:         linux at alteeve.com
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> Node Assassin:  http://nodeassassin.org
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