Since the release of VMware vSAN, people have been wondering what the difference is between VSA and vSAN. In fact, the difference between VSA and vSAN is about the same as the difference between a NAS and a SAN.
For a start, VSA has a maximum usable storage of 16TB, while VMware vSAN has no such restriction. VSA is scalable up to 3 hosts, while vSAN can be scaled out to the size of the vSphere cluster and has a minimum of 3 hosts.
There are also some significant performance differences. Firstly, VSA is a virtual appliance running on ESXi, while vSAN is an operating system in itself. Consequently vSAN manages its own resources, rather than having to request resources. This also means that is is more optimised.
Finally, VSA doesn’t support SSD caching and intelligent data placement, so vSAN has some large performance advantages here.
Put simply, the difference between VMware VSA and vSAN is that VSA is for small companies, whilst VMware vSAN is aimed at larger organisations.