how many paths are used to send data to a VMFS Datastore at any given time?

An administrator is configuring an ESX Host with 2 Fibre Channel HBAs. The attached FC Storage Array has two active Storage Processor ports. No zoning is configured. Using Round Robin multipathing, how many paths are used to send data to a VMFS Datastore at any given time?

A.
4

B.
1

C.
2

D.
3

Explanation:
Fibre Channel SAN Configuration Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 25.

Round Robin (RR) Uses a path selection algorithm that rotates through all available paths enabling
load balancing across the paths.

Round-Robin Load Balancing
VMware ESX Server 3.5, VMware ESX Server 3i version 3.5, VMware VirtualCenter 2.5, page 1

When one path from the ESX Server host to the SAN becomes unavailable, the host switches to another path. ESX Server hosts can also use multipathing for load balancing.

When to switch – Specify that the ESX Server host should attempt a path switch after a specified number of I/O blocks have been issued on a path or after a specified number of read or write commands have been issued on a path. If another path exists that meets the specified path policy for the target, the active path to the target is switched to the new path.

Since the active path is switched to a new path, it can be assumed that only a single path is ever used at any given time, (B above).