Rebuild RAID 5 Virtual Drive PowerEdge 830

Hi…this is in regard to a Dell PowerEdge 830, P4, @3GB ram, with a Perc 4e/DC UtlraScsi 320 controller, Raid 5, 4-swappable internal drives (D:, E:). There is also an external 1E, 4 drive Raid array (F:) I am in the process of rebuilding Disk 0:3 that failed using Dell OpenManage, with a new same sized Dell OEM drive for this server. However, it is VERY slow. Almost 45 min for each % of completion.

I can not take the second external array or server offline b/c of the need for user access (which is actually not much). Is this a normal speed? Why so slow?

Also, my first rebuild. Do I have to restart the server or something else in order to have the rebuilt virtual drive array re-appear as a valid drive when the rebuild is 100% complete?