Understanding and Designing Serviceguard Disaster Recovery Architectures

Figure 29 Extended Cross-Subnet Cluster with Two Data Centers and a Third Location with WDM

Links

Quorum Server

Data Center

Primary Data Center 2Primary Data Center 1

QS Node

Storage

Connections

Redundant

WDM Links frequently

Cross Subnet

Conﬁguration

Maximum distance

100 kilometers

Node A Node B

FC Switch

Router 3

Router 4

Node C Node D

Network Switch 1 Network Switch 2

Router 2

Router 1

DWDM

FC Switch

Storage Storage

Network Switch 3 Network Switch 4

FC Switch

WAN

DWDM

This example, figure 30 is an Extended Cross-Subnet Cluster. In Data Center 1, Switch 1 is for

subnet 192.168.1.0, and Switch 2 is for subnet 192.168.10.0. In Data Center 2, Switch 3 is for

subnet 192.168.2.0 and Switch 4 is for subnet 192.168.20.0. While it cannot be shown in this

diagram, each of these network switches has a Standby switch, bridged to it, and each node has

a Standby LAN connected to the Standby switches.To enable the Cross-subnet heartbeat to work,

subnets 192.168.1.0 and 192.168.2.0 must be statically routed to each other, and subnets

192.168.10.0 and 192.168.20.0 must be statically routed to each other. In this example Routers

1 and 3 are routed to each other and Routers 2 and 4 are routed to each other through the WAN.

These static routes are shown by the green lines to the WAN. You must ensure that the physical

routes between each pair of subnets do not pass through a common path, otherwise it results in a

single point of failure . In this example, the WDM boxes are only used for the storage interconnects

between the data centers, however the routers can be connected to the WDM boxes, rather than

the WAN. The WDM boxes connected between the two Primary Data Centers are configured with

redundant fiber links and the standby fiber feature is enabled. Cluster lock disks are not allowed

in this configuration. This configuration cannot include SGeRAC, CVM , or CFS (if SGeRAC, CVM,

or CFS is required, a Site Aware disaster recovery Architecture with a Metrocluster product is

Extended Distance Cluster on HP-UX 69