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 29 (page 68) 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

68 Extended Distance Cluster Configurations