i have a feeling you will not be able to VMotion between the nodes that do not see that LUN at the same HLU.
   Current 6 host ESX cluster, new 4 node/blade UCS being added into the same cluster.   We have setup and connected the 4 UCS servers to our CX4-480. All the new UCS servers have individual storage groups and currently one boot LUN 0 (boot from SAN).   I would like to add all other LUNs from the previous cluster to these 4 new storage groups. Currently there is already a LUN 0 (HLU) presented to the original cluster.   If I reassign the LUN 0 a different HLU when I add it to my new UCS storage groups will all be ok?   Maybe a VMWare question, but if I do this I will have 10 systems all accessing the same LUNS however 4 of them (new UCS) will have a different LUN 0 on the back end. It doesn't seem right.  I have backup systems accessing the cluster LUNs by different HLU numbers, however they aren't responsible for HA options and therefore needed in the true "clutered" scenario.    Let me know if you can explain, help me understand, it or direct me on this. Thanks.  
ESX - HLU/ALU 0 in cluster