Examples relate to an approximative memory deduplication method, a controller apparatus or controller device for a memory or storage controller, a memory or storage controller, a computer system and to a computer program. The approximative memory deduplication method comprises determining a hash value of a data block. The hash value is based on a user-defined approximative hashing function. The approximative memory deduplication method comprises storing a quantized version of the data block based on the hash value using a memory or storage device of the computer system.