HP serviceguard t2808-90006 Los Angeles Cluster, New York Cluster, Data Cent er a Data Center B

Disaster Tolerance and Recovery in a Serviceguard Cluster

Understanding Types of Disaster Tolerant Clusters

Figure 1-6 Continental Cluster

node 1b	node 2b
pkg A_R	pkg B_R
High Availability Network

Los Angeles Cluster:	WAN	New York Cluster:
Data Center A		Data Center B

node 1a	node 2a
pkg A	pkg B

Data Replication and/or Mirroring

Continentalclusters provides the flexibility to work with any data replication mechanism. It provides pre-integrated solutions that use HP StorageWorks Continuous Access XP, HP StorageWorks Continuous Access EVA, or EMC Symmetrix Remote Data Facility for data replication.

The points to consider when configuring a continental cluster over a WAN are:

•Inter-cluster connections are TCP/IP based.

•The physical connection is one or more leased lines managed by a common carrier. Common carriers cannot guarantee the same reliability that a dedicated physical cable can. The distance can introduce a time lag for data replication, which creates an issue with data currency. This could increase the cost by requiring higher speed WAN connections to improve data replication performance and reduce latency.

•Operational issues, such as working with different personnel trained on different processes, and conducting failover rehearsals, are made more difficult the further apart the nodes are in the cluster.

28 Chapter 1