Building a Disaster-proof Data Center with HP Serviceguard for Linux, June 2007

Figure 4. Two data center setup
Figure 4 shows a configuration that is supported with separate network and Fibre Channel links
between the data centers. In this configuration, the Fibre Channel 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 Fibre Channel links separate is that if
there is a link failure between sites, the ability to exchange heartbeats and the ability to write
mirrored data are not lost at the same time. This configuration is supported to a distance of 10 km
between data centers.
All the nodes in the extended distance cluster must be configured with the multipath feature of the
QLogic driver to provide redundancy in connectivity to the storage devices. Mirroring for the storage
is configured such that each half of the mirror (disk set) is be physically present at one data center.
Further, from each of the nodes, there are multiple paths to both of these mirror halves.
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