1. A method, in an array controller of a two-level hierarchical log structured array architecture for a non-volatile memory array, wherein the two-level hierarchical log structured array (LSA) architecture comprises an array-level LSA in the array controller and a node-level LSA in each node of the non-volatile memory array, for coordinated garbage collection, the method comprising: maintaining host logical block address (LBA) to node LBA mapping in an array controller connected to a plurality of nodes, wherein a host data processing system issues access requests to host LBA and wherein the mapping maps the host LBA space to a node LBA space of a plurality of nodes; making overprovisioned space in the node LBA space of the plurality of nodes available to the array-level LSA; adding additional overprovisioned space at each node LBA space; and initiating array-level garbage collection at the array-level LSA.