For redundant virtual drives (RAID 1, RAID 5, RAID 6, RAID 10) with hot spare drives assigned, when a drive fails, or when you remove a drive, the dedicated hot spare drive, if available, goes into the Rebuilding state with the virtual drive in the Degraded state. After rebuilding is complete, that drive goes to the Online state.
Cisco UCSM raises a disk missing and virtual drive mismatch fault because although the virtual drive is operational, it does not match the physical configuration that Cisco UCSM expects.
if you insert a new disk in the slot with the disk missing, automatic copy back starts from the earlier hot spare disk to the newly inserted disk. After copy back, the hot spare disk is restored. In this state all faults are cleared.
If automatic copy back does not start, and the newly inserted disk remains in the Unconfigured Good, JBOD, or Foreign Configuration state, remove the new disk from the slot, reinsert the earlier hot spare disk into the slot, and import foreign configuration. This initiates the rebuilding process and the drive state becomes Online. Now, insert the new disk in the hot spare slot and mark it as hot spare to match it exactly with the information available in Cisco UCSM.