Sata and sas on the same machine

You lucky fellow.

I can't give you a straight answer, but I can point you here - this site mentions that you can obtain a cable to connect 4x drives to a SAS connector. I'm not sure of the specifics of your server, but it possibly already contains one of said cables?

http://support.dell.com/support/edocs/storage/RAID/PERC6/en/UG/HTML/index.htm

Couldn't locate drive mixing in my brief search of the manual, but I am fairly certain you can mix drive types in the server/controller (SAS/SATA/SSD). You cannot mix drive types in the VDs (can't have a RAID 1 with a SAS and a SATA drive). It's been a few years , but I've used a MD 3000 before which was pre-PERC 6 and you could mix drive types in that enclosure (SAS/SATA) so I assume you can do the same with a later PERC. It shouldn't matter what your first VD drive type is either. I would typically make a RAID 1 SAS for the OS, then whatever else is required afterwards for the server.