US Patent 9454433 Adaptive rebuild scheduling scheme

Method and apparatus for redundant array of independent disks (RAID) recovery are disclosed. In one embodiment, a RAID controller schedules requests to rebuild failed drives based on the wear state of secondary drives and input/output (I/O) activity. The controller may be configured to assign higher scheduling priority to rebuild requests only when necessary, so as to reduce the time needed for the rebuild and to avoid affecting performance of the RAID system. In particular, the controller may give higher priority to rebuild requests if secondary drive failure is likely. In addition, the controller may determine when write-intensive periods occur, and assign lower priority to rebuild requests during such periods.