At VMworld 2015, VMware announced many new enhancements to Virtual SAN. One of which is that VSAN can now deliver highly available storage with just 2 physical nodes. This is known as 2 Node VSAN. Previously, to achieve redundancy for high availability, VSAN required 3 physical nodes. Here’s a nice post on this:
2 is the minimum number of hosts for VSAN if you ask me
At VMworld 2015, VMware also announced support for Virtual SAN for ROBO (Remote Office Branch Office) licensing to align with vSphere ROBO licensing. Like vSphere ROBO, VSAN for ROBO is sold in packs of 25 VMs that can be distributed across multiple sites. The great thing about this model is if you have 5 sites with each running 5 VM’s, you can purchase one 25 VM ROBO pack to support the 25 VM’s across the 5 sites. One limitation is that you cannot deploy a ROBO license on a site that will run more than 25 VMs.
There can be a bit of confusion between the deployment model and the license model because the 2 Node VSAN (which is often referred to as ROBO VSAN) and the VSAN for ROBO licensing are mutually exclusive. In other words, you can deploy a 2 Node vSphere cluster but apply VSAN Standard or VSAN Advanced licensing to enable VSAN on it. And, you can deploy a 3, 8, 17, or 64 node vSphere cluster and apply VSAN for ROBO licensing to enable VSAN on it. However, we expect that if you are deploying a 2 node vSphere cluster with VSAN enabled, you will likely apply a vSphere for ROBO and VSAN for ROBO license. I point this out because you may want to only deploy 2 nodes but want to run 50 VM’s. This is perfectly fine but would require VSAN Standard or VSAN Advanced licensing.
This post may further enhance what I’ve discussed:
Live Virtually 
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