The SAS 6/iR does not have any way to expand a virtual disk and it does not support multiple arrays across the disks.  In short ... you need to backup, delete, recreate, restore to replace disks with larger ones.
I just recently added two RAID 1 SAS 400 GB drives to replace two older small drives.  I replaced each one at a time until they were successfull resynchronized and the controller reported the RAID 1 virtual drive as "Optimal".   Trouble is that the Dell Storage Manager reports that the added space that I want to use as "Reserved Space" and the Windows Server 2003 Disk Manager does not see the reserved space as unallocated space so I can used it.  What in the world is "Reserved Space" and how do I get to use it or reclaim it?  Thant you all in advance.
SAS 6/ir Storage Manager reports reserved space on RAID 1 new drives, How do I 
use or reclaim the reserved space?.