Multi-tier caching

A method of storing data as a plurality of key-value pairs in a multi-tier storage system, the system comprising at least one lower-latency non-volatile memory storage device and at least one higher-latency non-volatile memory storage device, the method comprising:

• generating a first zone manager for managing a first partition of storage of a first non-volatile memory device among the lower-latency non-volatile memory storage devices to generate a tier of the multi-tier storage system;
• generating a second zone manager for managing a second partition of storage of a second non-volatile memory device among the higher-latency non-volatile memory storage devices to generate another tier of the multi-tier storage system;
• allocating, from a partition managed by the first zone manager, bytes pointed at by a first sub-list among all the key-value pairs in a key-value relation;
• allocating, from a partition managed by the second zone manager, bytes pointed at by a second sub-list among all the key-value pairs in the key-value relation;
• allocating bytes from the first zone manager for storing meta-data, where the meta-data comprises at least one association of the key-value relation with an array of pointers to sub-lists belonging to the relation,
• wherein each sub-list includes at least one pointer to bytes allocated for sorted key-value pairs comprising the corresponding sub-list, wherein each partition comprises at least one block of a given size, and
• wherein the system maintains a hierarchy structure in one of the tiers that stores the key-value relation and enables the key-value pairs to be stored in any one of the tiers.