Specifications

DATA CENTER BEST PRACTICES
SAN Design and Best Practices 36 of 84
at all. On most large scale arrays, the FC port that has been assigned to RDR is dedicated to only RDR and no
host trafc. Considering that the RDR port on the array can only communicate RDR trafc, there is no need to
run that port into the production fabric. There are valid reasons to have to go through a production fabric such
as IBM SVC, EMC CLARiiON (host shared FC port), tape applications, or connectivity of many arrays (more than
can be accommodated by the Brocade 7800 Extension Switch alone) over the same WAN infrastructure. A single
FCIP channel extender can be directly connected to both “A” and “B” controllers on the storage array, which is
known as a two-box solution. Alternatively, a channel extender is dedicated to the “A” controller and a different
channel extender dedicated to the “B” controller, which is known as a four-box solution. A single service
provider for both the “A” and “B” paths can be used, or different service providers can be used, depending on
the requirements of the organization and its tolerance to the recurring monthly costs of the additional WAN
connection. Figure 21 shows the two-box solution, and Figure 22 shows the four-box solution with a single
service provider.
fig22_SAN_Design
Production Site Back-Up Site
A FC FC
B
A
B
Storage
Array
Storage
Array
FCIP
Brocade
7800
Brocade
7800
WAN
IP Network
Figure 21. Two-box RDR solution directly connected to the storage array.
fig23_SAN_Design
Production Site Back-Up Site
A FC FC
B
A
B
Brocade
7800
Storage
Array
Storage
Array
FCIP
Brocade
7800
Brocade
7800
Brocade
7800
WAN
IP Network
Figure 22. Four-box RDR solution directly connected to the storage array.
It is also possible to incorporate the production fabrics into the FCIP path, although this is not recommended
unless there is a compelling reason to do so (Figure 23). Tape is most often the reason for attaching channel
extenders to a production fabric, providing greater connectivity to many devices. IBM SVC has requirements for
connectivity to the production fabric. Many customers prefer to connect channel extenders to the production
fabric when using EMC CLARiiON because MirrorView and SAN Copy applications that run on the array share
bandwidth with hosts over the same FC port; therefore, the production fabric is used to direct the trafc to the
hosts and to the channel extender.