When SATA and SAS drives are mixed in the same backplane/enclosure, inter-operability can arise. Strange issues have been encountered by several vendors when doing so.
The main problem is that sata and sas have different voltage levels. Some system integrators can boost the sata's voltage by using interposers.
If you look at the hardware user guide for the controller, you will find this statement on page 11/36.
The SAS controller allows you to use SATA II and SAS hard disk drives in the same system, so you can take advantage of the benefits of each type of drive; however, Intel does not recommend mixing SAS and SATA II drives in the same enclosure.
Note: you may get an error message from Intel Raid Web Console 2 if doing so as well:
189 : SAS/SATA mixing not supported in enclosure;
All the best,
Thanks for a good explanation regarding this issue.