HP Serviceguard Extended Distance Cluster for Linux A.01.01 Deployment Guide, Third Edition, May 2008

Disaster Tolerance and Recovery in a Serviceguard Cluster
Understanding Types of Disaster Tolerant Clusters
Chapter 1 25
"objective" can be set for the recovery point such that if data is
updated for a period less than the objective, automated failover can
occur and a package will start. If the time is longer than the
objective, then the package will not start. In a Linux environment,
this is a user configurable parameter: RPO_TARGET.
• Extended Distance Cluster disk reads may outperform CLX in
normal operations. On the other hand, CLX data resynchronization
and recovery performance are better than Extended Distance
Cluster.
Continental Cluster
A continental cluster provides an alternative disaster tolerant
solution in which distinct clusters can be separated by large distances,
with wide area networking used between them. Continental cluster
architecture is implemented using the Continentalclusters product,
described fully in Chapter 2 of the Designing Disaster Tolerant HA
Clusters Using Metrocluster and Continentalclusters user’s guide. This
product is available only on HP-UX and not on Linux. The design is
implemented with two distinct Serviceguard clusters that can be located
in different geographic areas with the same or different subnet
configuration. In this architecture, each cluster maintains its own
quorum, so an arbitrator data center is not used for a continental cluster.
A continental cluster can use any WAN connection through a TCP/IP
protocol; however, due to data replication needs, high speed connections
such as T1 or T3/E3 leased lines or switched lines may be required. See
Figure 1-6.
NOTE A continental cluster can also be built using multiple clusters that
communicate over shorter distances using a conventional LAN.