Really depends on your requirements. You could use the VSA. You could also use an additional server with local storage in a raid to present to ESXi via NFS. It works great. Don't expect P4000 performance from the solution but it would work just fine. VMware solutions are limited to VSA and in the future VSAN but both have a cost associated. I have seen some really neat setups with some SSD for cache used as well.
Depends on budget and requirements.