Compaq 112726-001 - ProLiant - 6500 Integration Notes page 7

Failover and Recovery States
Figure 2 illustrates the failover and recovery process. If no communication between the servers
can be established across any of the three lines of communication, the server that has lost
connections to the network and storage will enter failover state. At the same time, the other node,
in this case, Server B, will enter the recovery state (Figure 2A). Upon entering the recovery state,
Server B assumes responsibility for Server A volumes and clients (Figure 2B). Security and
licensing are maintained by transferring NDS rights to the surviving server. Total failover time
corresponds to the time necessary to detect the failure and complete the failover process. During a
failover, the remaining server must mount the new volumes, launch any active server-based
applications that were running on the failed device, and transfer security and license information.
NHAS also allows manual failover of shared volumes at any time by pressing F at the NHAS
console. By forcing a failover, you can remove a server from the network for scheduled
maintenance without interrupting access to that server's volumes.
Disabled Server
Figure 2. Failover and Recovery
0096-0699-A
Accessed by Accessed by
Node B only Node B only
Volume 1 Volume 2
Compaq RAID Array 4000
Fibre Channel Arbitrated Loop
Fibre Channel Storage Hub
Dedicated Interserver Direct Link
Local Area Network
Network Clients
A. Node B Entering Recovery State
Server
Node B
NetWare
Interconnects
Data
Inter-server Monitoring
Data and Monitoring
Volume A Volume B
Server A Server B
Logical Connections
B. Node B Assuming
Responsibility for
Node A's Volumes