Yep that's it then, you need to have shared Fibre Channel or iSCSI storage for vMotion, DRS and HA to work. They all operate on the premise that all ESX hosts can see the vmdk files etc and that in the case of vMotion or DRS al that is being copied across the vMotion network is the VM's active memory and state information otherwise it would take too long to copy a 10Gb vmdk from one host to another and in the meantime the Guest OS in the VM would be unresponsive. For HA shared storage is required as it is intended for use in a hardware failure scenario, so if you had an esx host fail due to a hardware failure (RAM, CPU etc) then the server will just crash, in that case ESX will not get time to copy VMs off to another ESX host, it'll just be turned off by the hardware going donw, bringing the VMs sitting on it's local disk with it. With shared disk, the ESX host will still go down but the other ESX host can see the VMs still sitting on the shared storage and start them back up.
