12 Recovering From Disk Failures
Figure 3-2. Rebuilding a RAID 5 disk group
If you had installed a global hot spare allocated to the same PERC adapter of 
the failed disk, the RAID group will automatically switch the role of the failed 
disk with the hot-spare disk, and begin the rebuild operation automatically. In 
this case, you would need to replace the failed disk and assign it as the new 
global hot spare for that PERC adapter. Refer to the "Assign and Unassign 
Hot Spares" section of the OpenManage™ Server Administrator's User's Guide 
for more information on global hot spares. 
About RAID 5 Degraded Mode 
When a failed hard drive is replaced, the RAID group begins an automatic 
rebuild operation. During this operation, data and parity information is 
reallocated across all hard drives in the RAID group. Until the rebuild 
completes, performance of the RAID group is degraded. You should continue 
to monitor the status of the rebuild to ensure it completes successfully. 
  NOTE: If another hard drive fails while the RAID group is rebuilding, all data on that 
RAID group may be lost.