Setting up RAID5 with three SAS Disks.. Need two partitions.

Hi, 

I have three SAS disks and I wish to set RAID 5 and have two partitions, one for the System and one for Data. Currently I am doing the following:

In Array Configuration Utility:

1. I create one array with the three disks

2. The SAS array is created. 

3.  When the array is created, I then create the first logical drive. This is my C: System drive in Windows. 

4. Then within the same array I create a second logical drive. This will then be my D: drive in Windows. 

I then run HP Intelligent Provisioning and let it install Windows for me... This works but I'm not sure it's the best way. Am I doing something wrong?