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From Andy Piper <>
Subject RE: Clustering - JGroups issues and others
Date Wed, 19 Oct 2005 15:08:33 GMT
At 02:40 AM 10/19/2005, wrote:
>It is the problem of "homogenius" environment. Blade servers are
>naturally organized in chassis called enclosures (HP's term) or
>bladecenters (IBM's one). All those chassis are interconnected with each
>other using one or more external switches. Due to the fact that larger
>solutions tend to use multiple VLANs, the failure of each of them can be
>independent from the others. So it can occur, that the group of nodes
>will loose connectivity to all the rest of the cluster for some time (HA
>implied), but will see each other and also other backend services like
>database etc.

This is the split-brain problem. If the split is even you basically 
can't solve the singleton issue without backdoor communication 
channels. If the split is not even you can reach consensus on who 
owns the data, but it basically means that the other part of your 
cluster has to fence itself and is unusable.


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