I added 1 extra disk to a RAID5 Data partition on R720 server, Windows 2008, Perc H710 Mini.  Reconfigured using Server Administrator and the extra space shows up on the Data partition I'm adding too.   And it's contiguous(shows up right next to existing partition in Disk Management).

BUT in the Windows disk Management software the ability to "Extend Volume" is greyed out.    

I rescanned disks and rebooted the server.  Option still greyed out.

One disk in the existing RAID5 was a non Dell Certified disk, would that stop the ability to extend volume?

Otherwise out of ideas right now.   Thinking of using 3rd party software to expand/extend the RAID5 volume.

Thanks.

Dan