RAID 5 IBM Netfinity Server -DISK ID 0 DEFUNCT

In RAID 5 having 4 disk and 1 hotswappable Disk case,when disk id 0 gets DEFUNCT ,then does the system goes down?Please get some URL Links or Solutions where it can be Briefly explained that whether it is DISk 0 OR DISK ID 1 RAID 5 by replacing it by hot swap what solve the problem!!!ITS URGENT
Thanks in Advance