What you will need to do is install Open Manage Server Administrator on the server. That may require a reboot. Then put the new HDDs in and from inside OMSA you can go to the Virtual Disk and select to reconfigure. It will allow you to select the new drives to add to the VD. Once that process is complete you will need to use a utility like diskpart to actually extend the partition on the windows side. Also like you mentioned it is vital to make sure you do a backup before this process just to be safe. Please let me know if you have any further questions as I would be happy to assist.
Hi All,  I have a PERC H800 and MD1200 RAID6'd on a PE 2970 on Windows Server 2008 R2 64x.  Currently I have eight 2 TB SAS drives, but have 4 slots open and would like to expand.  Is it as simple as adding 4 drives? After backing up the data of course...  Any help appreciated.
Can I expand my MD1200 RAID6 configuration?