HP Serviceguard Extended Distance Cluster for Linux A.11.20.10 Deployment Guide, December 2012

centers is connected to both the nodes via two FC switches in order to provide multiple paths. This
configuration supports a distance up to 100 kms between datacenter1 and datacenter2.
Figure 4 Two Data Center Setup
Figure 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.
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.
Also note that the networking in the configuration shown is the minimum. Added network connections
for additional heartbeats are recommended.
2.2 Types of Data Link for Storage and Networking
Fibre Channel technology lets you increase the distance between the components in an Serviceguard
cluster, thus making it possible to design a disaster recovery architecture. The following table shows
some of the distances possible with a few of the available technologies, including some of the
Fiber Optic alternatives.
Table 2 Link Technologies and Distances
Maximum Distance SupportedType of Link
50 metersGigabit Ethernet Twisted Pair
500 metersShort Wave Fiber
10 kilometersLong Wave Fiber
100 kilometersDense Wave Division Multiplexing (DWDM)
16 Building an Extended Distance Cluster Using Serviceguard and Software RAID