Understanding and Designing Serviceguard Disaster Recovery Architectures

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 25 (page 63) 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 3

(page 49), Table 4 (page 49) and Table 5 (page 51) for details).

Extended Distance Cluster configurations with Two Data Centers and a Third Location 63