There are some cluster-level prerequisites that must be satisfied before VSAN can be enabled. As we have already discussed, you will need a minimum of three hosts, with a minimum of one SSD and one spinning disk or capacity-tier SSD per host. This is probably optional, but it would help with 5.5/6.0 convergence of the text.
In addition, the following prerequisites need to be satisfied:
Disable vSphere HA
Tagging disks as SSDs if using RAID-0 mode
You should be logged in to the vSphere Web Client as an administrator or user, authorized to alter cluster-level settings. All VSAN operations must be executed via the vSphere Web Client. The legacy vSphere Client is not supported for VSAN operations.