Data management in solid state storage devices

A method for controlling a solid state storage device in which a solid state storage in the solid state storage device comprises erasable blocks each erasable block comprising a plurality of data write locations, the method comprising:

• storing input data in successive groups of data write locations, each group of data write locations in the successive groups of data write locations comprising write locations in a set of erasable blocks in each of a plurality of logical subdivisions of the solid state storage;
• error correction encoding the input data such that each group of data write locations contains an error correction code for the input data in that group of data write locations;
• maintaining, in memory of the solid state storage device, metadata indicating a location of the input data in the solid state storage;
• maintaining an indication of validity of data stored in each data write location;
• prior to erasing an erasable block, selecting an erasable block from the set of erasable blocks for erasing in dependence on a number of write locations containing invalid data in the group of data write locations which contain write locations in that erasable block;
• and
• recovering valid data from each group of data write locations containing write locations in that erasable block thereby forming recovered valid data and re-store the recovered valid data as new input data.