Yes you read that right, you can actually use shared storage in a vCenter without the use of a NAS or physical SAN all you need is VSAN, virtual storage area network, this is a software defined storage solution from VMware. How it works is when you setup vSAN all the drives in your host aggregate together forming a large storage pool the entire cluster can use. It is important to note on vSAN hosts you have cache drives, used for read caching and write buffering usually high speed disk such as SSD, then capacity drives, used for long term storage of data no need to be as fast as cache think HDD, SSD will work. With vSAN you can even create disk groups for each host, each disk group requires at least 1 cache drive and 1-7 capacity drives, you can have up to 5 disk groups per host. Your most likely limitation in terms of disk groups per host will likely be the amount of capacity drives you have on the host as well as the total number of disks you have on the host. Of course you can always choose to have only one disk group per host. The main reason you would have multiple disk groups on one host is if the maximum number of drives you could have in 1 disk group, 8, would be exceeded, having multiple disk groups on one vSAN host allows you to contribute more storage.