Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building an Extended Distance Cluster Using MC/ServiceGuard
Guidelines on DWDM Links for Network and Data
Chapter 266
Guidelines on DWDM Links for Network and
Data
• The network interfaces used must support DLPI (link level).
There must be less than 200 milliseconds of latency in the network
between the data centers.
No routing is allowed for the networks between the data centers.
The maximum distance supported between the data centers for
DWDM configurations is 100 kilometers.
Both the networking and Fibre Channel Data Replication can go
through the same DWDM box - separate DWDM boxes are not
required.
Since DWDM converters are typically designed to be fault tolerant, it
is acceptable to use only one DWDM box (in each data center) for the
links between each data center. However, for the highest
availability, it is recommended to use two separate DWDM boxes (in
each data center) for the links between each data center. If using a
single DWDM box for the links between each data center the
redundant standby fibre link feature of the DWDM box must be
configured. If the DWDM box supports multiple active DWDM links,
that feature can be used instead of the redundant standby feature.
At least two dark fibre optic links are required between each
Primary data center, each fibre link routed differently to prevent the
“backhoe problem.” It is allowable to have only a single fibre link
routed from each Primary data center to the third location, however
in order to survive the loss of a link between a Primary data center
and the third data center, the network routing should be configured
so that a Primary data center can also reach the Arbitrator via a
route passing through the other Primary data center.
The network switches in the configuration must support DLPI (link
level) packets. The network switch can be 100BaseT (TX or FX),
1000BaseT (TX or FX) or FDDI. The connection between the
network switch and the DWDM box must be fibre optic.
FibreChannel switches must be used in a DWDM configuration;
FibreChannel hubs are not supported. Direct Fabric Attach mode
must be used for the ports connected to the DWDM link.