You cannot "reconfigure" a Virtual Disk TO or FROM a "nested" RAID level (RAID 10, 50, 60).  Unfortunately, in order to make your existing 8-disk RAID 10 a 10-disk RAID 10, you will need to wipe it out and configure anew.  <ADMIN NOTE: Broken link has been removed from this post by Dell>  
Trying add another mirror to the RAID 10 set on my H800 in a R710 that's attached to a MD1220 enclosure. There is no reconfigure option from the Virtual Disk area of Server Manager that the documentation says should be there. Currently I have an 8 disk RAID 10 in the MD1220 and two (certified) disks that are spun up unused that I need to incorporate on the fly. They are all in the MD1220. How is this done? Hoping this doesn't need to be a destroy and recreate routine. Thanks
H800 in R710 RAID 10 expansion