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

Lars Marowsky-Bree
2005-05-02T21:01:01Z

On 2005-04-30T07:12:46, Daniel Phillips <phillips@istop.com> wrote:

> process. And obviously, there already is some reliable starting point or
> cman would not work. So let's just expose that and have a better cluster
> stack.

Most memberships internally construct such a fixed starting point from
voting or other 'chatty' techniques.

This is exposed by the membership (providing all nodes in the same order
on all nodes), however the node level membership does not necessarily
reflect the service/application level membership. So to get it right,
you essentially have to run such an algorithm at that level again too.

True enough it would be helpful if the group membership service provided
such, but here we're at the node level.

> But note that it _can_ use the oldest cluster member as a recovery
> master, or to designate a recovery master. It can, and should - there
> is no excuse for making this any more complex than it needs to be.

The oldest node might not be running that particular service, or it
might not be healthy. To figure that out, you need to vote.

This is straying a bit from LKML issues, maybe it ought to be moved to
one of the clustering lists.

Sincerely,
Lars Marowsky-Brée <lmb@suse.de>

--
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business -- Charles Darwin
"Ignorance more frequently begets confidence than does knowledge"