You cannot directly start a rebuild on most controllers - you will need to assign the offline/failed disk as a hot-spare ... the rebuild should then begin within a few minutes.
I have a Raid 1 configuration on my Dell Server.  OpenManager is reporting that my virtual disk is "degraded".  I've run diag on both hard drives and they both pass.  The server boots, but it's running very slow.  Any advise would be appreciated.  Thanks!
Virtual Disk "Degraded" Hard Drives Pass Diag