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

Lars Marowsky-Bree
2005-04-28T12:55:36Z

On 2005-04-27T22:52:55, Daniel Phillips <phillips@istop.com> 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@suse.de>

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High Availability & Clustering
SUSE Labs, Research and Development
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