With the introduction of VSANs, the network administrator can build a single topology containing switches, links, and one or more VSANs. Each VSAN in this topology has the same operation and property of a SAN. A VSAN has the following additional features:
Multiple VSANs can share the same physical topology.
The same Fibre Channel IDs (FC IDs) can be assigned to a host in another VSAN, which increases VSAN scalability.
Every instance of a VSAN runs all required protocols such as FSPF, domain manager, and zoning.
Fabric-related configurations in one VSAN do not affect the associated traffic in another VSAN.
Events causing traffic disruptions in one VSAN are contained within that VSAN and are not propagated to other VSANs.
The following figure shows a fabric with three switches, one on each floor. The geographic location of the switches and the attached devices is independent of their segmentation into logical VSANs. No communication between VSANs is possible. Within each VSAN, all members can talk to one another.
Figure 1. Logical VSAN Segmentation
The application servers or storage arrays can be connected to the switch using Fibre Channel or virtual Fibre Channel interfaces. A VSAN can include a mixture of Fibre Channel and virtual Fibre Channel interfaces.
The following figure shows a physical Fibre Channel switching infrastructure with two defined VSANs: VSAN 2 (dashed) and VSAN 7 (solid). VSAN 2 includes hosts H1 and H2, application servers AS2 and AS3, and storage arrays SA1 and SA4. VSAN 7 connects H3, AS1, SA2, and SA3.
Figure 2. Example of Two VSANs
The four switches in this network are interconnected by VSAN trunk links that carry both VSAN 2 and
VSAN 7 traffic. You can configure a different inter-switch topology for each VSAN. In the preceding figure, the inter-switch topology is identical for VSAN 2 and VSAN 7.
Without VSANs, a network administrator would need separate switches and links for separate SANs. By enabling VSANs, the same switches and links may be shared by multiple VSANs. VSANs allow SANs to be built on port granularity instead of switch granularity. The preceding figure illustrates that a VSAN is a group of hosts or storage devices that communicate with each other using a virtual topology defined on the physical SAN.
The criteria for creating such groups differ based on the VSAN topology: