ESSS_Coelho,   You're correct in assuming that you would have to recreate, being that the SSD and non SSD can't be mixed in the same virtual disk. As far as how to configure, my opinion is it best to separate the OS from the data, so I too would go with the 2 drive raid 1 for the OS, and the remainder for the data/VM's. As far as the differences in VMFS5 and VMFS6, I found this page that lays it out fairly clearly, which can be found here.   Let me know if this helps.       
Hi guys, just a question about the virtual disks.My PowerEdge R530 currently has 6 non-ssd disks installed and 2 bays without disks (8 bays total). I'm noticing a certain sluggishness in the applications and I thought about replacing all non-ssd disks with ssd disks. It is possible? I understand that I will have to recreate the virtual disk and reinstall vmware. Right? My atual VMFS type is VMFS5, what is the major difference in VMFS5 and VMFS6? Or would it be better to leave 2 non-ssd disks for raid1 (VMware OS) and the other 6 bays use ssd disks for the VMs volumes (of course creating a new virtual/raid volume for that)? Thanks!
R530 Non-SSD Disks