Have recently started down the Mellanox hardware road with our new primary whitebox Hyper-V 2016 cluster running Storage Spaces Direct on Mellanox 2700 switches.  Super excited.  As we were going through the design and purchasing faze for our new Co-Lo infrastructure I fought to start process of migrating off of Cisco chassis based switches (7k's, 9k's) with whitebox switches.  I lost some of that battle (moving off of cisco) but succeeded in moving to fixed port based modular switches.  This article somewhat explains my viewpoint on this:  http://www.mellanox.com/blog/2018/04/why-leaf-spine-networks-taking-off/