Rules for Separate Network and Data Links

The network interfaces used must support DLPI (link level).

There must be less than 200 milliseconds of latency in the network between the data centers.

No routing is allowed for the networks between the data centers.

The maximum distance between the data centers for this type of configuration is currently limited by the maximum distance supported for the networking type or Fibre Channel link type being used, whichever is shorter.

Currently, FDDI offers a total ring length of 100 kilometers, so this will allow up to 50 kilometers between data centers for both two and three data center solutions.

There can be a maximum of 500 meters between the Fibre Channel hubs or switches in the two data centers if Short-wave ports are used. This distance can be increased to 10 kilometers by using a Long-wave Fibre Channel port on the hubs or switches. The distance can be increased to 80 kilometers if Finisar (Long-haul) GBICs are used in Fibre Channel switches (hubs are not supported for this distance). If DWDM links are used, the maximum distance between the data centers is 100 kilometers.

There must be at least two alternately routed networking links between each Primary data center to prevent the "backhoe problem." The "backhoe problem" can occur when all cables are routed through a single trench and a tractor on a construction job severs all cables and disables all communications between the data centers. It is allowable to have only a single network link routed from each Primary data center to the Arbitrator data center, however in order to survive the loss of the network link between a Primary data center and the Arbitrator data center, the network routing should be configured so that a Primary data center can also reach the Arbitrator via a route which passes through the other Primary data center.

There must be at least two alternately routed Fibre Channel Data Replication links between each data center. In three data center configurations, no Fibre Channel Data Replication links are required for the Arbitrator data center.

Fibre Channel hubs are only supported for distances up to 10 kilometers. For distances longer than 10 kilometers, Fibre Channel switches are required. Fibre Channel switches are always the preferred solution, since they offer much better performance than Fibre Channel hubs, which only support Fibre Channel Arbitrated loop mode.

Refer to the HP 9000 Servers Configuration Guide (available through your HP representative) for a list of supported FibreChannel hardware.