US Patent 11372562 Group-based RAID-1 implementation in multi-RAID configured storage array

A storage system that supports multiple RAID levels presents storage objects with front-end tracks corresponding to back-end tracks on non-volatile drives and accesses the drives using a single type of back-end allocation unit that is larger than a back-end track. When the number of members of a protection group of a RAID level does not align with the back-end allocation unit, multiple back-end tracks are grouped and accessed using a single IO. The number of back-end tracks in a group is selected to align with the back-end allocation unit size. If the front-end tracks are variable size, then front-end tracks may be destaged into a smaller number of grouped back-end tracks in a single IO.