Specifications
DATA CENTER BEST PRACTICES
SAN Design and Best Practices 32 of 84
•As edge fabrics and the routed network grow, the use of “lters” such as LSAN zone binding and LSAN tagging
can improve topology convergence time and efcient usage of FCR resources.
•Make the backbone fabrics redundant to improve resiliency. This means redundancy for each fabric; therefore,
fabric A would be redundant and so would fabric B. Fabric B would never be used as the redundancy for fabric
A, and vice-versa.
•Backbone fabrics that share connections to the same edge fabrics must have unique backbone fabric IDs.
This statement is referring to the case in which there are multiple “A” fabrics and multiple “B” fabrics. This
does not refer to sharing connections between A and B fabrics.
•TI Zones within the backbone fabric cannot contain more than one Destination Router Port (DRP) per
each fabric.
•TI over FCR is supported only from edge fabric to edge fabric. Trafc isolation from backbone to edge is
not supported.
•UltraScale ICLs on the core blade cannot be used for FCR.
VIRTUAL FABRICS TOPOLOGIES
The Brocade FOS Virtual Fabrics (VF) feature provides a mechanism for partitioning and sharing hardware
resources, with the intention of providing more efcient use, deterministic paths for FCIP, increased fault
isolation, and improved scalability. Virtual Fabrics use hardware-level fabric isolation between Logical Switches
(LSs) and fabrics. Logical Fabrics consist of one or more Logical Switches across multiple physical switches
(non-partitioned).
Hardware-level fabric isolation is accomplished through the concept of a Logical Switch, which provides
the ability to partition physical switch ports into one or more “logical” switches. Logical Switches are then
connected to form Logical Fabrics. As the number of available ports on a switch continues to grow, partitioning
switches gives storage administrators the ability to take advantage of high-port-count switches by dividing
physical switches into different Logical Switches. Without VF, an FC switch is limited to 256 ports. A storage
administrator can then connect Logical Switches through various types of ISLs to create one or more
Logical Fabrics.
There are three ways to connect Logical Switches: a traditional ISL, IFL (EX_Port used by FCR), and Extended
ISL (XISL). An ISL can only be used for normal L2 trafc between the connected Logical Switches, carrying only
data trafc within the Logical Fabric of which the ISL is a member. One advantage of Virtual Fabrics is that
Logical Switches can share a common physical connection, and each LS does not require a dedicated ISL.
In order for multiple Logical Switches, in multiple Logical Fabrics, to share an ISL, Virtual Fabrics supports an
XISL connection, which is a physical connection between two base switches. Base switches are a special type
of Logical Switch that are specically intended for intra- and inter-fabric communication. As mentioned, base
switches are connected via XISLs and form the base fabric.
Once a base fabric is formed, the Virtual Fabric determines all of the Logical Switches and Logical Fabrics
that are physically associated via the base fabric, as well as the possible routes between them. For each local
Logical Switch, a Logical ISL (LISL) is created for every destination Logical Switch in the same Virtual Fabric that
is reachable via the base fabric. Thus, an XISL comprises the physical link between base switches and all of the
virtual connections associated with that link. In addition to XISL support, the base fabric also supports IFLs via
EX_Port connections for communication between Virtual Fabrics. Base switches also interoperate with FC router
switches, either in the base fabric or in separate backbone fabrics.
VF Guidelines
If no local switching is used, any set of ports in the chassis/fabric can be used to create a Virtual Fabric. If local
switching is used, ports for the VF fabric should be from the same port groups.