1. A method comprising: applying a RAID data redundancy scheme to a plurality of non-volatile solid-state memories in a storage subsystem, including defining a RAID group from among the plurality of non-volatile solid-state memories, by executing a data layout engine that is external to the storage subsystem, wherein the storage subsystem does not include any data layout engine for accessing the non-volatile solid-state memory; and in response to a read request for a set of data, identifying a RAID group of the plurality of non-volatile solid-state memories, in which requested data is stored; determining whether a non-volatile solid-state memory in the identified RAID group is busy; and when a non-volatile solid-state memory in the identified RAID group is busy, reading data of the set of data from the other non-volatile solid-state memories in the identified RAID group and reconstructing the set of data from the data read from the other non-volatile solid-state memories in the identified RAID group.