Assign disk 0 as a hot-spare to begin the rebuild.  You might consider running diagnostics to see if the drive is healthy - if it is bad, then you can replace it; if it is good, then make sure your system firmware (BIOS, ESM, PERC, HDD) is up-to-date.
We have a PowerEdge T110 with a PERC S300 RAID card and two 456GB SATA drives.  The server hung one night and when it rebooted it gave a warning that the virtual disk was degraded.  When we view the virtual disk from OpenManage, it shows Physical Disk 0:1 as the only disk with status Online.  When we view the physical disks it shows Physical Disk 0:0 with status Ready and Physical Disk 0:1 with status Online. How can we join the Physical Disk 0:0 to the virtual disk so that it will mirror the other disk and bring the virtual disk out of the "degraded" state? We've done a Rescan but that did not change anything.  Both physical disks have a green checkmark beside them.  Other than the "degraded" warning on the virtual disk, there are no other warnings or errors on the server. Any advice is appreciated.  Thanks!
How to add physical disk to RAID 1 virtual disk