Understanding and Designing Serviceguard Disaster Recovery Architectures

Refer to Figure 25 (page 64) for an example of an Extended Distance Cluster configuration in two

data centers with a third location.

Figure 25 Extended Distance Cluster with Two Data Centers

Node A Node B

Heartbeat Networks

over FDDI

Fibre Links For

Software Mirroring

Data Replication

Maximum distance

50 kilometers

Node C Node D

Storage

Site 1 Site 2

Storage

Network Switch Network Switch

FC Switch

Cluster Lock Cluster Lock

In the figure 26, Finisar (long haul) GBICs and cabling that supports up to 80 kilometers are used

for the ISL links between the Fibre Channel switches in the two data centers. The Inter switch links

between the Ethernet switches use GBICs and cabling that the switch vendor supports for up to

100 kilometers. The total distance supported between the two data centers are determined by the

shorter of the maximum distances supported for the ISLs by the Fibre Channel switch and Ethernet

switch vendors (not to exceed 100 kilometers). In this example, the distance between the data

centers is limited to 80 kilometers. The redundant network and Fibre Channel links between the

two data centers must be routed geographically differently, such that if the cables in one trench

are severed, the cables in the alternately routed trench will still provide both network and Fibre

Channel connectivity and allow the cluster to continue normally. This cluster is not allowed to

contain more than four nodes for Serviceguard clusters (due to the cluster lock limitation of four

nodes). For EC RAC clusters, the number of nodes allowed and the maximum distance supported

will vary, depending upon the HP UX revision and the volume manager being used (see Table 2

(page 51), Table 3 (page 51) and Table 4 (page 53) for details).

64 Extended Distance Cluster Configurations