Redundant data storage schemes for multi-die memory systems

A data storage apparatus, comprising:

• an interface, which is configured to communicate with a memory that includes at least N memory units;
• and
• a processor, which is configured to define a mapping between logical addresses and respective physical storage locations in the memory units, to select a set of N logical addresses, which are mapped to N respective physical storage locations in different ones of the memory units, such that K of the logical addresses in the set, 1≧K<N, are assigned for data storage and N−K logical addresses in the set, other than the K logical addresses, accept data for storage in the K logical addresses in the set, to compute the redundancy information for the data to store the data in the K logical addresses at a first storage density, and to store the redundancy information in the N−K logical addresses at a second storage density that is lower than the first storage density.