R640 PERC H730P - mix SAS and SATA drives?

Hi.

I have a PowerEdge R640 with a PERC H730P controller, and the 8x 2.5inch chassis. Currently the system has 2x SAS 10k HDD in RAID1.

Is it possible to install SATA HDD in the other 6 positions (as a separate RAID volume), or can I only use SAS? Most online sources seem to say that mixing SAS and SATA is fine, so long as they are not in the same RAID array.

The user manual seems to support this, saying "Combining SAS and SATA drives in the same RAID volume is not supported" (which implies it is supported in different volumes). But then later on the same manual says "Mixing of 2.5 inch 10K or 15K SAS drives with 2.5 inch 7.2K SATA or Nearline SAS drives on the same backplane is not supported". Which seems pretty clear, but taken together leaves me confused. Or does it mean 5.4k SATA drives would be ok (seems odd...)?

Can anyone clear this up? Thanks in advance.