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ExpressCluster X 3.1 for Linux Getting Started Guide - Nec

ExpressCluster X 3.1 for Linux Getting Started Guide - Nec

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Chapter 1 What is a cluster system?Normal OperationOccurrence of FailureFailoverOperationOperationServer FailureOperation TransferFailbackRecovering ServerOperationOperationFigure 1-2: From occurrence of a failure to recoveryWhen the specification of the failover destination server does not meet the system requirements oroverload occurs due to multi-directional stand-by, operations on the original server are preferred.In such a case, a failback takes place to resume operations on the original server.A stand-by mode where there is one operation and no operation is active on the stand-by server, asshown in Figure 1-3, is referred to as uni-directional stand-by. A stand-by mode where there aretwo or more operations with each server of the cluster serving as both active and stand-by servers isreferred to as multi-directional stand-by.Normal OperationNormal OperationActiveServerStand-byServerActive Server <strong>for</strong>Operation AStand-by Server <strong>for</strong>Operation BActive Server <strong>for</strong>Operation BStand-by Server <strong>for</strong>Operation AOperationOperation AOperation BFigure 1-3: HA cluster topology18<strong>ExpressCluster</strong> X <strong>3.1</strong> <strong>for</strong> <strong>Linux</strong> <strong>Getting</strong> <strong>Started</strong> <strong>Guide</strong>

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