#Check a host for any Fibre Channel devices that are not set to Round Robin.  Modify to check clusters if needed.
Get-VMhost VMHOSTNAME | Get-VMHostHba -Type "FibreChannel" | Get-ScsiLun -LunType disk | Where { $_.MultipathPolicy -notlike "RoundRobin" } | Select CanonicalName,MultipathPolicy

#Set the Multipathing Policy on a host to Round Robin for any Fibre Channel devices that are not Round Robin
$scsilun = Get-VMhost VMHOSTNAME | Get-VMHostHba -Type "FibreChannel" | Get-ScsiLun -LunType disk | Where { $_.MultipathPolicy -notlike "RoundRobin" }
Set-ScsiLun -ScsiLun $scsilun -MultipathPolicy RoundRobin