Worth reading : VMFS-5 VMFS-3, What’s the Deal? » boche.net – VMware vEvangelist
- You will use VMFS3 if you have a vSphere environment which is mix of vSphere 4.x (also 3.x) & 5.x hosts. Presently VMFS5 datastores cannot be accessible to hosts running an ESXi version less than vSphere 5.0