Although the documentation specifies the customer should back etcd with nvme/ssd storage, I do not believe it is thorough enough in declaring how the nvme/ssd should be attached. 

I have had experiences with some TAMs and Architects that are using "loopholes" in the documentation to justify using some form of "network" attached storage to back etcd. Justification typically revolves around that networked storage being backed by nvme/ssd. Customers are designing solutions using FC or Ceph based storage, and although network attached, it isn't specifically excluded like "iSCSI".

I believe specifying "direct attached" or "local storage" may help close those loopholes.

This largely only affects on-prem customers.