Re: [PATCH 1b/7] dlm: core locking

From: Daniel McNeil
Date: Thu Apr 28 2005 - 11:42:17 EST

On Thu, 2005-04-28 at 05:33, Lars Marowsky-Bree wrote:
> On 2005-04-27T22:26:38, David Teigland <teigland@xxxxxxxxxx> wrote:
> > > And, I assume that the delivery of a "node down" membership event
> > > implies that said node also has been fenced.
> > Typically it does if you're combining the dlm with something that requires
> > fencing (like a file system). Fencing isn't relevant to the dlm itself,
> > though, since the dlm software isn't touching any storage.
> Ack. Good point, I was thinking too much in terms of GFS/OCFS2 here ;-)

Since a DLM is a distributed lock manager, its usage is entirely for
locking some shared resource (might not be storage, might be shared
state, shared data, etc). If the DLM can grant a lock, but not
guarantee that other nodes (including the ones that have been kicked
out of the cluster membership) do not have a conflicting DLM lock, then
any applications that depend on the DLM for protection/coordination
be in trouble. Doesn't the GFS code depend on the DLM not being
recovered until after fencing of dead nodes?

Is there a existing DLM that does not depend on fencing? (you said
yours was modeled after the VMS DLM, didn't they depend on fencing?)

How would an application use a DLM that does not depend on fencing?



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