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

[Lars Marowsky-Bree]

On 2005-04-27T22:52:55, Daniel Phillips <phillips@xxxxxxxxx> wrote:

> > So we can't deliver it raw membership events. Noted.
> 
> Just to pick a nit: there is no way to be sure a membership event might not 
> still be on the way to the dead node, however the rest of the cluster knows 
> the node is dead and can ignore it, in theory.  (In practice, only (g)dlm and 
> gfs are well glued into the cman membership protocol, and other components, 
> e.g., cluster block devices and applications, need to be looked at with 
> squinty eyes.)

I'm sorry, I don't get what you are saying here. Could you please
clarify?

"Membership even on the way to the dead node"? ie, you mean that the
(now dead) node hasn't acknowledged a previous membership which still
included it, because it died inbetween? Well, sure, membership is never
certain at all; it's always in transition, essentially, because we can
only detect faults some time after the fact. 

(It'd be cool if we could mandate nodes to pre-announce failures by a
couple of seconds, alas I think that's a feature you'll only find in an
OSDL requirement document, rated as "prio 1" ;-)

I also don't understand what you're saying in the second part. How are
gdlm/gfs "well glued" into the CMAN membership protocol, and what are we
looking for when we turn our squinty eyes to applications...?


Sincerely,
    Lars Marowsky-Brée <lmb@xxxxxxx>

-- 
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business

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