Q: I have two host bus adapters on my Hyper-V server. Should I create one or two virtual SANs?
A: If your Hyper-V server has two paths (uplinks) to the SAN via two separate host bus adapters (HBAs), then there are two choices:
- Create one virtual SAN and attach both HBAs to it.
- Create two virtual SANs, each with one HBA connected.
In both cases you create two virtual Fibre Channel adapters for the virtual machine, then either attach to the single virtual SAN or one to each of the virtual SANs. You then use Multipath I/O within the virtual machine to give resiliency in connectivity to the SAN.
Generally, the best practice is to use the first option because the virtual Fibre Channel adapters would be distributed among the available uplinks even though they're connected to the same virtual SAN because a round-robin algorithm is used for uplink assignment. The benefit of the single virtual SAN approach is that if an uplink is unavailable, then both virtual Fibre Channel adapters would still be connected and therefore not hamper the startup or migration of virtual machines.
The second approach of two separate virtual SANs would be used if you needed to guarantee that each virtual port (virtual Fibre Channel adapter) was connected to a separate fabric.