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From <>
Subject RE: Clustering - JGroups issues and others
Date Tue, 18 Oct 2005 11:47:22 GMT

Here is my 5 cents... I have some comments regarding clustering based on
J-Groups. We were trying to use this technology and came to certain
points, that render it unusable in our case.

Many of the cluster caches/replicates assume that all the information
propagated to all the nodes in the cluster. Some of the solutions
propagate only keys, however. In any case this solution can not be used
in sufficiently large clusters as the rate of upates would eat all the
node capacity making it unusable.
Regarding J-Groups itself. Probably that is specific to cluster
facilities in JBoss, but generally J-Groups organize a list of nodes,
and every node checks the state of the next one in the chain. The
problem is that in many cases servers may fail/disconnect in groups,
which causes two problems: the segmentation of the cluster and
extremelly high failure report time, as for architectures based on blade
technology servers shut down in large packs and it really takes time to
detect several sequentally disconnected servers.

To overcome the problems we ended up with the "star" architecture, where
the central node is responsible for maintaining the list of other nodes.
The availability of the central node itself could be provided with
facilities like Red Hat Cluster Suite or similar (service failover,
floating IPs, etc).


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