US Patent 9513845 Memory module virtualization

A memory system having a plurality of modules operated so that a group of memory modules may operation in a RAID configuration having an erase hiding property. The RAID groups are mapped to areas of memory in each of the memory modules of the RAID group. More than one RAID group may be mapped to a memory module and the erase operations of the RAID groups coordinated such that the erase operations do not overlap. This may improve the utilization of a bus over which the memory module communicates with the controller. Where a memory module is replaced by a memory module having an increased storage capacity, the additional storage capacity may be mapped to an expanded logical address space.