01-03-2018 05:18 AM
Welcome to the Community Forums.
OEM specification intended for storage is the one M.2 SSD / PCIe 3.0 x 4 and one HDD / SATA 6.0Gb/s, 2.5" wide, 7mm high port.
Other m.2 PCie port is for the 11ac, 2x2, Wi-Fi + Bluetooth combo adapter, M.2 Card (2230) and is not certified for storage but rather for wireless features instead.
Hope this helps answer your query.