Disaster Tolerance and Recovery in a Serviceguard Cluster

Disaster Tolerant Architecture Guidelines

Disaster Tolerant Local Area Networking

Ethernet networks can also be used to connect nodes in a disaster tolerant architecture within the following guidelines:

•Each node is connected to redundant switches and bridges using two Ethernet host adapters. Bridges, repeaters, or other components that convert from copper to fibre cable may be used to span longer distances.

Disaster Tolerant Wide Area Networking

Disaster tolerant networking for continental clusters is directly tied to the data replication method. In addition to the redundant lines connecting the remote nodes, you also need to consider what bandwidth you need to support the data replication method you have chosen. A continental cluster that handles a high number of transactions per minute will not only require a highly available network, but also one with a large amount of bandwidth.

This is a brief discussion of things to consider when choosing the network configuration for your continental cluster. Details on WAN choices and configurations can be found in Continental Cluster documentation available from: http://docs.hp.com -> High Availability.

•Bandwidth affects the rate of data replication, and therefore the currency of the data should there be the need to switch control to another site. The greater the number of transactions you process, the more bandwidth you will need. The following connection types offer differing amounts of bandwidth:

—T1 and T3: low end

—ISDN and DSL: medium bandwidth

—ATM: high end

•Reliability affects whether or not data replication happens, and therefore the consistency of the data should you need to fail over to the recovery cluster. Redundant leased lines should be used, and should be from two different common carriers, if possible.

•Cost influences both bandwidth and reliability. Higher bandwidth and dual leased lines cost more. It is best to address data consistency issues first by installing redundant lines, then weigh the price of data currency and select the line speed accordingly.

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Chapter 1