Understanding and Designing Serviceguard Disaster Recovery Architectures

Figure 2 Disaster Recovery Architecture

packages A and B fail

over to Data Center B

Client Connections

Replication Link

Node 1

Data Center A Fails

Node 2

Node 3

Node 4

Data Center A Data Center B

pkg A

pkg C

pkg A

pkg D

pkg B

pkg C

pkg D

Node 1

Node 2

Node 3

Node 4

pkg B

Understanding types of disaster recovery clusters

To protect against multiple points of failure, cluster components must be geographically dispersed:

nodes can be put in different rooms, on different floors of a building, or even in separate buildings

or separate cities. The distance between the nodes is dependent on the types of disaster from which

you need protection, and on the technology used to replicate data. Three types of disaster-recovery

clusters, that is, Extended distance clusters, metropolitan clusters and Continental clusters are

described in this guide.

These types differ from a simple local cluster in many ways. Extended distance clusters and

metropolitan clusters often require right-of-way from local governments or utilities to lay network

and data replication cable. This must be taken into consideration during the design and

implementation phases. They also require a different kind of control mechanism to avoid data

integrity issues, such as a quorum server. Typically, metropolitan clusters use an arbitrator site

containing a quorum server node or additional cluster nodes instead of cluster locks. Continental

clusters span great distances and operate by replicating data between two completely separate

local clusters.

8 Disaster Recovery in a Serviceguard Cluster