[Linux-cluster] Re: Linux-cluster Digest, Preventing LVM from concurrent access

[Rafael Micó Miranda]

Hi Edson,

El jue, 27-08-2009 a las 12:14 -0300, Edson Marquezani Filho escribió:
> Ok, after a while, things is starting to work here. I have defined a
> service, with a lvm-cluster resource, and my (still very simple)
> script that launchs the VM and destroys them. Service is moved from
> one server to another, when some goes down, and VM are recreated.
> 
> But, I could launch the same VM (with the same LV as its disk)
> manually on the slave node, even though it was mounted on master. I
> guess that it was expected, right?, once you have warned about that
> before.
> 
> "Actually it would not avoid an admin doing, by hand, an erratic mount
> but a bugzilla ticket has been opened by Brem Belguebli to fix an LVM
> issue that is causing that behaviour."
> 

Yes, you can bypass the exclusive flag by hand if you dont take it into
account when activating the exclusive LV on a second node.

While the exclusive LV is mounted in other node, the command "lvchange
-aey XXX/YYY" should give you an error message. "lvchange -ay XXX/YYY"
will bypass it.

> But, rgmanager was able to mount it on both servers simultaneosly too.
> I runned a test, disconecting the heartbeat link, making one server to
> be fenced, and the VM launched on the "winner" as expected. But when
> the "loser" server came back, still without heartbeat link, it
> launched the same VM again, and service appeared as running locally on
> boths nodes. I guess lvm-cluster should avoid this, shouldn't ?
> 

This should not happen. Have you set "exclusive=yes" into the resource
definitions in cluster.conf? Can we have a copy of your current
cluster.conf?

> I have not understood, because this behauvior is the same as if I had
> not defined any lvm or lvm-cluster resource to the service. Both nodes
> see the LV, anyway, and could mount it whenever them want.
> 
> What could be wrong?
> 
> Besides that, I can't relocate the service to another node by hand,
> with clusvcadm, what causes the service to fail and become inactive,
> forcing me to disable and enable it again.
> 

I tested it and it should work. Same answer as before: give us a copy of
your current cluster.conf.


> Thanks.
> 
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Cheers,

Rafael

-- 
Rafael Micó Miranda