From the latest docs ive read i get the sense this is still required, and would function as a write cache only. If i have 3 PCIE SSDs in each host, each capable of about 8000Mbps read and 3000 Write, I am put off by the concept of adding a single caching drive, even if optane for writes. The hosts will be connected 100gb ethernet.
Is the caching tier still required? It seems to only hurt write performance in this scenario. Is it still required and am i missing something?
Yes, unfortunately. As mentioned during VMworld, a new architecture where a caching layer is not needed is considered for future release of vSAN. When/If that will be available is something I cannot comment on.