  Yes. Assign the disk as a hot-spare (Global or Dedicated). I know you said you already did, but that is all you can do, and the process is the same from the controller's BIOS utility. If it is not rebuilding, it is probably because it is not a valid hot-spare for any configured VD: Is the drive actually showing that it is still configured a hot-spare? It actually succeeded in assigning it as a hot-spare?
Hi, this is my situation regarding RAID5 array. Problem is on Dell Power Edge 2900 server with PERC 6/i controller. Last week one of 4 disks in RAID5 array failed due the power cut off and VD is still online but degraded. Server OS MS 2003 works and data is OK. I've replaced failed HDD with brand new (same model but not certified by dell), and PERC 6/i controller did not start rebuilding process automatically. I've read on this pages that is necessary to assign new HDD as Global Hot Spare to begin rebuild process, and I did this but VD is still showing only 3 online drives and status degraded. I didn't tray to start rebuilding process from BIOS because currently can't afford downtime. Is there a way to start rebuilding process from within OMSA - latest version installed or I have to enter BIOS RAID controller management?  Also I've try to assign this new HDD as a Global Hot Spare and as Dedicated Hot Spare with no result. Please advise what to do because I can't confirm that this Hot Spare will step in correctly if another HDD fails.  Physical Disk 0:0:0 Online  Physical Disk 0:0:1 Online Physical Disk 0:0:2 Online Physical Disk 0:0:3 Ready Global Hot Spare 
PowerEdge 2900 one of 4 disk failed in RAID 5 array