If a disk is faulty, the process of recovering data on the faulty disk is typically done through a process called reconstruction. Reconstruction involves copying data from a healthy disk in a RAID array to the faulty disk. This can be done through software or hardware RAID controllers. The RAID controller will use the data stored on the other disks in the RAID set to recreate the data that was stored on the faulty disk. This process can be done while the RAID array is online, allowing the RAID to continue functioning while the reconstruction process is taking place. Once the reconstruction is complete, the faulty disk can be replaced and the RAID array can continue to function normally.

In active-standby mode, only one controller works at a time and if one controller is faulty, services are not affected. In active-active mode, both controllers are active and the service failover is more efficient than in active-standby mode.