This is a question I've been pondering for awhile and never got a clear answer. I know VMware lists Storage APIs for Array Integration/MPIO as an Enterprise and Enterprise+ license feature, but its been my experience that a vendor supplied PSP plugins (Nimbles NCM, EqualLogic MEM, etc) seem to install fine on Hosts licensed for Essentials Plus and above. I was surprised after discovering this, and even more so after finding that all available paths were active and working as expected.
I hadn't thought about it for awhile until I noticed in Nimble's 2.1.x guide it just lists ESXi 5.x Hosts with no license level requirement.
Anybody else ever notice this? Is this one of those "it works, but isn't supported" type of deals?