The option in Data Protector Transportation mode: SAN is not exclusive (the backup will continue), if SAN transport method fails then we will use the remaining transport methods available that Vmware API VixDiskLib_ConnectEx() passes to Data Protector.
If all the transport methods are available then it will choose the one that you selected in the Backup specification, otherwise it will continue through all the list of available methods using the following list defined by VixDiskLib_ConnectEx(): san:hotadd:nbdssl:nbd