HP Serviceguard Extended Distance Cluster for Linux A.01.01 Deployment Guide, Third Edition, May 2008

Building an Extended Distance Cluster Using Serviceguard and Software RAID
Guidelines on DWDM Links for Network and Data
Chapter 256
Guidelines on DWDM Links for Network and
Data
• 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.
• Routing is allowed to the third data center if a Quorum Server is
used in that data center.
• 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 fiber 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 fiber optic.