VSANs

VSANs isolate servers and storage devices that are physically connected to the same fabric, therefore allowing creating of logical SAN islands on a shared hardware. Each VSAN effectively functions as a separate SAN. VSAN is a Cisco proprietary feature.

Each VSAN has its own fabric services completely isolated from fabric services in other VSANs. For instance: FCID Domain Manager, FCNS Name Server, FSPF, Zoning, Port Security database. Fabric Events are isolvated per-VSAN basis.

VSANs have the same purpose as VLANs.

Each VSAN has its own:

1. Domain IDs and Principal Switch priority
2. Node FCIDs
3. Zones and Zonesets
4. FSPF routing topology
5. Load-balancing method across FSPF Equal Cost paths and across FC-Port Channel individual links
6. Time-out values
7. in-order-guarantee setting
8. Interop mode. This feature is used when other non-Cisco storage switches are connected to a port in a VSAN.

A maximum of 256  VSANs can be configured, but allowed VSAN IDs are from 1 to4093. VSAN 1 is default and cannot be removed. VSAN 4094 is always isolated and is used for those ports for which VSAN was just deleted. These ports should be manually reassigned to an active VSAN.

I have to configure VSANs manually on each MDS switch. CFS does not distribute VSANs between switches. I am not required to configure each VSAN on every MDS switch. If an MDS switch has no FC interfaces in a given VSAN and will not carry any transit traffic for that VSAN then I don't need to configure it on the switch.

Port VSAN membership on the switch is assigned on a port-by-port basis either manually (by configuring VSAN database on  a switch) or dynamically (Dynamic Port VSAN Membership=DPVM). SAN-OS checks the DPVM database during a device FLOGI and assigns it to a specific VSAN based on the device port's pWWN or nWWN. DPVM can be distributed between MDS switches with CFS. DPVM is not supported on TL and FL ports. It is only supported on F ports. Dynamy Port VSAN Membership (DPVM) is also referred to as WWN-Based VSANs or Dynamic VSANs.

When activating PDVM database, I should always use the force keyword.Otherwise, if nWWN or pWWWN entry in the database overlaps with an nWWN or pWWN of an aready active N_Port on any of the switches, the dpvm commit will fail.

Show vsan membership does not reflect DPVM configuration, this command displays ony static VSAN assignments. Instead, use show interface brief - it displays the active VSAN ID for each port whether it was assigned statically or dynamically.