HP serviceguard t2808-90006 manual Creating Highly Available Networking, Alternative Power Sources

Disaster Tolerance and Recovery in a Serviceguard Cluster

Disaster Tolerant Architecture Guidelines

Figure 1-9 Alternative Power Sources

Power Circuit 1 node 1

Power Circuit 2

node 2

Data Center A

node 3 Power Circuit 3

Power Circuit 4

node 4

Data Center B

Housing remote nodes in another building often implies they are powered by a different circuit, so it is especially important to make sure all nodes are powered from a different source if the disaster tolerant cluster is located in two data centers in the same building. Some disaster tolerant designs go as far as making sure that their redundant power source is supplied by a different power substation on the grid. This adds protection against large-scale power failures, such as brown-outs, sabotage, or electrical storms.

Creating Highly Available Networking

Standard high-availability guidelines require redundant networks. Redundant networks may be highly available, but they are not disaster tolerant if a single accident can interrupt both network connections. For example, if you use the same trench to lay cables for both networks, you do not have a disaster tolerant architecture because a single accident, such as a backhoe digging in the wrong place, can sever both cables at once, making automated failover during a disaster impossible.

In a disaster tolerant architecture, the reliability of the network is paramount. To reduce the likelihood of a single accident causing both networks to fail, redundant network cables should be installed so that they use physically different routes for each network. How you route cables will depend on the networking technology you use. Specific guidelines for some network technologies are listed here.

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