A VSAN is a Cisco proprietary security mechanism, which can be compared to VLANs for the networks. VSANs can further increase security for storage and servers by allowing only the physical member ports of storage and servers to physically access each other. As with VLANs, if a port on the same fabric switch is not part of a VSAN, it will not have access to SAN.

There are number of ways that SAN could be connected with UCS servers, which include the following:

• Cisco FC MDS switches: MDS switches are Cisco FC SAN connectivity switches. These switches deal with the SAN protocols and are recommended in large-scale environments requiring a dedicated SAN infrastructure.
• FC module expansion or unified ports in Cisco Nexus switches: Cisco Nexus 5000 series switches provide FC module expansion to provide FC ports with SAN connectivity. The newer 5500/5600 series switches have unified ports like the Fabric Interconnects, which can be configured as Ethernet, FC, or FCoE. These switches are recommended for medium to large-scale infrastructures.
• Direct with Fabric Interconnects: The Fabric Interconnect provides unified ports, which can be configured as Ethernet, FC, or FCoE, and hence storage can be directly attached with the Fabric Interconnects. This is recommended for a small-scale deployment.
• Third-party fabric switches: Fabric switches from other vendors, such as Brocade, can also be used to connect storage to Cisco UCS.