Herbhoakes, From a performance standpoint the best option is not to split the virtual drives at the controller level, but instead create 2 arrays, a 2 drive raid 1 for the OS to use, then create a raid 5 with the remainder of the drives. This is all dependent on how many drives you have. Once that is done then you can place multiple PARTITIONS on the virtual disk. So you have intact arrays with multiple partitions on it, instead of a split virtual drive with individual partitions on it. Plus with splitting the array at the controller level can risk you having data loss. If you only have the Raid 5 then you can partition it into different disks from the OS, but it isn't recommended to split it at the controller.
I have a Dell R420 with a PERC H310 RAID controller.  This controller allows me to create either one Virtual disk using all of the available space in the RAID 5 array or it allows you to build two Virtual disks that split the RAID 5 array space. If I create one virtual disk, and install Windows 2008, this presents to the OS as one physical disk.  I could then use the OS to partition the space into a C Drive and an D Drive. (both on the same "physical" disk). If I create two virtual disks and install Windows 2008, this presents to the OS as two physical disks.  I could put the C drive on the first "physical" disk and the D drive on the second "physical" disk. Are either of these options better than the other from a performance or other perspective, or are they about the same? 
Create 1 large or 2 smaller virtual disks?