[Linux-cluster] DLM locks with 1 node on 2 node cluster

[Zelikov_Mikhail at emc.com]

I checked that I have to following in the cluster.conf
<cman expected_votes="1" two_nodes="1">

I also checked that I do not loose the quorum with one node:

[root at bof227] clustat
Member Status: Quorate

  Member Name                              Status
  ------ ----                              ------
  bof227                                   Online, Local, rgmanager
  bof226                                   Offline


-----Original Message-----
From: David Teigland [mailto:teigland at redhat.com] 
Sent: Monday, August 28, 2006 1:05 PM
To: Zelikov, Mikhail
Cc: linux-cluster at redhat.com
Subject: Re: [Linux-cluster] DLM locks with 1 node on 2 node cluster

On Mon, Aug 28, 2006 at 11:41:55AM -0400, Zelikov_Mikhail at emc.com wrote:
> I am using the latest cluster from RHEL4 branch. I have 2 node cluster:
> nodes A and B. Node A grabs a lock in the exclusive mode, node B waits 
> for a membership change. I manually reset node A at which point node B 
> gets the membership change notification and then tries to acquire the 
> lock in the exclusive mode. At this point this operations locks 
> forever. Once the node A is up DLM returns with the lock acquired for node
B - as expected.
> However, if I shutdown node A instead of killing it then everything 
> works as expected - Node B gets the notification and the successfully 
> grabs the lock w/o locking up.

> Has anybody else seen this? I was wondering if this is a bug or there 
> is something special about 2-node clusters, or do I misunderstand how 
> it supposed to work?

You're probably not using cman's two_node setting which means the one node
by itself will be blocked by quorum.  When you do a 'cman_tool leave
remove', that reduces the votes required for quorum, so it's not a problem
for the remaining node.  Try using the two_node mode as described here:
  http://sources.redhat.com/cluster/doc/usage.txt

Dave