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

Disaster Tolerance and Recovery in an MC/ServiceGuard Cluster

Disaster Tolerant Architecture Guidelines

Chapter 1 39

Disaster Tolerant Local Area Networking

The configurations described in this section are for FDDI and Ethernet

based Local Area Networks.

Figure 1-10 Reliability of the Network is Paramount

If you use FDDI networking, you may want to use one of these

configurations, or a combination of the two:

• Each node has two SAS (Single Attach Station) host adapters with

redundant concentrators and a different dual FDDI ring connected to

each adapter. As per disaster tolerant architecture guidelines, each

ring must use a physically different route.

• Each node has two DAS (Dual Attach Station) host adapters, with

each adapter connected to a different FDDI bypass switch. The

optical bypass switch is used so that a node failure does not bring the

entire FDDI ring down. Each switch is connected to a different FDDI

ring, and the rings are installed along physically different routes.

node 1a node 2a

Data Center A Data Center B

node 1 node 2

node 1a node 2a

Data Center A Data Center B

node 1 node 2

Accident severs both network cables.

Accident severs one network cable.

Wrong:

Cables use

same route.

Right:

Cables use

different route.

Disaster recovery impossible.

Disaster recovery still possible.