A: In VMware vSphere versions prior to vSphere 5.0, the process to correctly configure multipath iSCSI required at least one step at the command line. This command-line step was often forgotten, and as a result many environments aren't enjoying the full benefits of multipath iSCSI.
vSphere 5.0 eases this process somewhat by eliminating the command-line step, replacing it with a GUI console that itself contains verification to ensure you've configured everything correctly. However, the process still requires a few steps.
First, in the vSphere Client, create a vSwitch that contains two VMkernel ports (with a different IP addresses for each port) for use by iSCSI. Connect multiple physical NICs to this vSwitch. When you've completed this step, view the properties of each VMkernel port and navigate to the NIC Teaming tab. Select Override switch failover order and arrange the adapters so that exactly one adapter is active for each VMkernel port. All other adapters should be set to Unused.
Next, navigate to Storage Adapters and view properties of the iSCSI Software Adapter. Select the Network Configuration tab, then click Add to create a new network configuration that binds each of the earlier VMkernel ports to the iSCSI Software Adapter.
You'll know you've done everything correctly if the tab's Port Group Policy reads Compliant.