Compaq ProLiant 6500 Deploying the ProLiant Cluster for NetWare 4.2 - Page 6

'HSOR\LQJ WKH 3UR/LDQW &OXVWHU IRU 1HW:DUH   The Failover Process Costandby State During normal operation, shown in Figure 1, each server node in the ProLiant Cluster for NetWare 4.2 operates as if it were a completely independent entity on the network. Server A and Server B are allocated their own dedicated volumes on the Compaq RAID Array 4000 shared storage. NHAS controls access for the shared storage and prevents one server from accessing the other server's volume. This controlling mechanism is vital to the operation of the cluster, since it prevents a split-brain scenario, wherein two servers may try to access the same data simultaneously; obviously, this could result in data corruption. In the given configuration, each server is operating in the costandby state, that is, independently but waiting for the other server to fail. Accessed by Node A only Accessed by Node B only Volume 1 Volume 2 Compaq RAID Array 4000 Server Node A Fibre Channel Storage Hub Fibre Channel Arbitrated Loop Dedicated Interserver Direct Link Server Node B Local Area Network NetWare Interconnects Volume A Volume B Server A Server B Logical Connections Network Clients Data Inter-server Monitoring Data and Monitoring Figure 1. ProLiant Cluster for NetWare 4.2 Costandby State 0096-0699-A