It doesn't matter which slots the disks are in ... just choose Reconfigure from your Virtual Disks menu, and you will be presented with a list of available disks - you will select those two drives and a target RAID level of RAID 5, and off you go.  It will take several hours for it to complete the Reconfigure.
I have a situation similar to this post: [URL]#19678204 I inherited a PowerEdge 2800, PERC 4e/Di running the following configuration: Virt Disk 0:  RAID-5, 3 disks, 2x 33.87GB, 1x 279.38GB (only 33.87GB used for RAID) C: drive is configured on VDisk 0 and is at about 1GB free space Can I simply add two more same model & (Dell Ready) 279GB drives one at a time, let them sync, then span the extra space for C: using Partition Manager?  Steve
How to add additional larger drives to RAID-5 array on PERC 4e/Di which is also 
System Drive C:?