Redundant Array Of Inexpensive Disks

How to rebuild RAID without obstructing data migration?

I see why RAID rebuilds obstruct data migration. A RAID rebuild is NOT like backup and restore. The rebuild consumes resources, e.g. CPU etc. So if we have the RAID on a separate system (managed by its own CPU) then: Surely this allows a RAID rebuild without obstructing data migration? Do you...