Could someone point me to a document that clear states mixed stack limits? I know that pure SSD stack is restricted to 4 shelves, but at least one document claims 6 shelves in mixed stack (it is internal document so I'm happy to discuss it offline if appropriate). HWU shows limits for SAS/SATA/SSD separately, but again is silent about mixed usage.
I would say HWU should explicitly describe limits in this case.
