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

Disaster Tolerance and Recovery in an MC/ServiceGuard Cluster

Types of Disaster Tolerant Clusters

Chapter 1 23

maximum distance between nodes in an extended distance cluster is set

by the limits of the data replication technology and networking limits.

An extended distance cluster is shown in Figure 1-3.

Figure 1-3 Extended Distance Cluster

Architecture requirements for several types of extended distance clusters

are described more fully in Chapter 2. Extended distance clusters can be

configured over shorter distances using FibreChannel mass storage, or

over distances as great as 100 km using storage and networking routed

over links extended via DWDM.

Metropolitan Cluster

A metropolitan cluster is a cluster that has alternate nodes located in

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. The architectural requirements are the same

as for an extended distance cluster, with the additional constraint of the

third location. And as with a campus cluster, the distance separating the

nodes in a metropolitan cluster is limited by the data replication and

network technology available.

NOTE While it is possible to configure physical data replication through

products such as HP’s XP Series disk arrays with Continuous Access XP

or Symmetrix EMC SRDF, it is still necessary to provide for high

availability at the local level through RAID or mirroring.

node 1

node 2

pkg A

pkg B

Data Center A Data Center B

Highly Available Network

Disk Mirroring

Highly Available Network

node 3 node 4

pkg C pkg D