Disaster Tolerance and Recovery in a Serviceguard Cluster
Understanding Types of Disaster Tolerant Clusters
Figure 1-4 | Two Data Center Setup |
Figure 1-4 shows a configuration that is supported with separate network and FC links between the data centers. In this configuration, the FC links and the Ethernet networks are not carried over DWDM links. But each of these links is duplicated between the two data centers, for redundancy. The disadvantage of having the network and the FC links separate is that if there is a link failure between sites, the ability to exchange heartbeats and the ability to write mirrored data will not be lost at the same time. This configuration is supported to a distance of 10 kms between data centers.
All the nodes in the extended distance cluster must be configured with QLogic driver’s multipath feature in order to provide redundancy in connectivity to the storage devices. Mirroring for the storage is configured such that each half of the mirror (disk set) will be physically present at one datacenter each. Further, from each of the nodes there are multiple paths to both of these mirror halves.