Understanding and Designing Serviceguard Disaster Recovery Architectures

2 Metrocluster and Continentalclusters
Understanding Metrocluster
Metropolitan Cluster
A metropolitan cluster is a cluster that has alternate nodes located in two different parts of a city
or in adjacent cities. Putting nodes further apart increases the likelihood that alternate nodes will
be available for failover in the event of a disaster. A Metropolitan cluster requires a third location
for arbitrator nodes or a quorum server. The distance separating the nodes in a metropolitan cluster
is limited by the data replication and network technology available. Each primary site must have
the same number of nodes.
NOTE: While it is possible to configure physical data replication through products such as HP’s
disk arrays with Continuous Access XP or P9000, Continuous Access EVA or P6000, 3PAR Remote
Copy or EMC’s SRDF, it is still necessary to provide for high availability at the local level through
RAID or mirroring.
In addition, there is no specification on how far the third location has to be from the two main
data centers. The third location can be as close as the room next door with its own power source
or can be as far as in a site across town. The distance between all three locations dictates the level
of disaster recovery a metropolitan cluster can provide.
Metropolitan cluster architecture is implemented through the following HP products:
• Metrocluster with Continuous Access for P9000 and XP
• Metrocluster with Continuous Access EVA
• Metrocluster with EMC SRDF
• Metrocluster with 3PAR Remote Copy
20 Metrocluster and Continentalclusters