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Re: [Linux-cluster] Starter Cluster / GFS



Jonathan Barber wrote:
On 11 November 2010 10:46, Gordan Bobic <gordan bobich net> wrote:
Jankowski, Chris wrote:
Gordan,

I did not ask for bonding.  This should work.  I asked for
multiple independent links - different networking interfaces
configured for different IP subnets mapping to different VLANS.

STP is, these days, run on a per VLAN basis. Having multiple
links in different VLANs protects against important classes of
network failures.  Bonded interface does not do it. This must
be integrated in the clustering software.
I don't quite see the point you're making. If your goal is redundant
networking, then you can achieve that by having bonded interfaces in each
node, and each of the components of the bonded interface should go to a
different switch. That will give you both extra bandwidth and a redundant
path between all the nodes, which will ensure you don't end up with a
partitioned cluster.

Chris' point is that if the STP has to recalculate (for example if the
STP root node dies), then having multiple interfaces in the same VLAN
will not help (if the time taken to recalculate is longer than the
fencing timeout). But, if he can run the heartbeat across multiple
VLANs, and the network supports per-VLAN STP, then he lowers the risk
of both VLANs being affected by the same event and therefore reduces
the likelihood of a shootout between the cluster nodes.

Of course, it depends on the topology of the STP domains as to whether
you are guaranteed to maintain at least one path between nodes in the
cluster given a STP node failure.

Yes, but your cluster VLAN (the one that's monitored for heartbeating) should be isolated, rather than public, so the only nodes on it will be the cluster nodes (and probably the SAN). If with that many nodes your spanning tree recalculation still takes 40 seconds you have network gear that is unfit for purpose anyway.

Gordan


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