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Disaster Tolerance and Recovery in a Serviceguard Cluster
Disaster Tolerant Architecture Guidelines
Chapter 146
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.