Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building a Metropolitan Cluster Using MetroCluster/CA
Designing a Disaster Tolerant Architecture for use with MetroCluster/CA
Chapter 3 79
Example Failover Scenarios with One Arbitrator
Taking a node off-line for planned maintenance is treated the same as a
node failure in these scenarios. Study these scenarios to make sure you
do not put your cluster at risk during planned maintenance.
Figure 3-2 Failover Scenario with a Single Arbitrator
The scenarios in Table 3-3, based on Figure 3-2, illustrate possible
results if one or more nodes fail in a configuration with a single
arbitrator.
node 1
pkg A
Data Center A
node 2
pkg B
A
B
D
1
C
1
CA links
Third Location
node 3
pkg C
Data Center B
node 4
pkg D
C
D
B
1
A
1
arbitrator 1
Table 3-3 Node Failure Scenarios with One Arbitrator
Failure Quorum Result
arbitrator 1 4 of 5 (80%) no change
node 1 4 of 5 (80%) pkg A switches
node 1, then node 2 3 of 4 (75%) pkg A and B
switch
node 1, 2, then arbitrator 1 2 of 3 (67%) pkg A and B
switch