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Re: [Linux-cluster] Re: cman multihome setup deprecated?



On Tue, 2005-11-08 at 11:45 +0100, Axel Thimm wrote:
> On Mon, Nov 07, 2005 at 03:22:04PM +0000, Patrick Caulfield wrote:
> > Axel Thimm wrote:
> > > Is this functionality deprecated and to be removed in a future update?
> > > Or does it need some work to be republished?
> > > 
> > > What is the recommended precedure for having a dedicated cluster
> > > network with a failover setup over a secondary network? E.g. I have
> > > all cluster nodes connected over two network, the client ("LAN")
> > > network, and a dedicated cluster network ("cluster-net").
> > > 
> > > What I'd like to achive it to have high-performance by allowing
> > > cman/dlm to have its own network, but also high-availablity by using
> > > the "LAN" network when the "cluster-net" fails, e.g. broken cable or
> > > broken switch.
> > 
> > "deprecated" isn't quite the right word! But I'm not sure what is.
> 
> "in works" ? :)
> 
> > As it stands, cman in RHEL4 supports multihome. The problem is that the DLM
> > doesn't so it's not much use in most environments.
> 
> So what would be the impact if the primary network breaks down? cman
> continues to operate happily, e.g. the heartbeat works, the cluster
> remains quorate etc., but GFS cannot operate its locks anymore?
> 
> Would that harm more than it would help? I.e. should I better
> implement multihoming on a lower level, e.g. a dynamic router on each
> node?
> 
Patrick could correct me if I am wrong, but I believe the plan here is
to use the totem redundant ring protocol from the openais project.  This
basically uses two or more networks and duplicates packets over both
networks.  If any element in one of the networks is faulty, the packet
data will still be delivered through the remaining network.

This is far superior to bonding, since the totem RRP is smart enough to
know which packets are duplicate and actually detects network failures,
instead of simply link failures.

Regards
-steve


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