A storage system forms an allocation unit for writing into solid-state storage memory. The allocation unit is formed from at least a portion of a first erase block and a first sub block of a partitioned second erase block. The system forms multiple subsequent allocation units. Each subsequent allocation unit is formed from a remaining second sub block of a partitioned erase block and at least a portion of a next erase block. Forming the subsequent allocation units consumes each of multiple erase blocks in a cascading sequence. The system allocates the allocation unit and the subsequent allocation units for writing in the storage system.