Data storage

A data storage device (e.g. cache memory) comprises an array of data storage elements (e.g. cache lines) arranged as multiple partitions of two or more data storage elements; each data storage element being associated with a respective identifier (e.g. cache tag) which identifies a data item currently stored by that data storage element; a predictor compares, for each partition, information derived from the identifiers associated with the data storage elements (e.g. combined hashes of tags) of that partition with information derived from an identifier associated with the required data item, to identify a subset of partitions that do not store the required data item; and a comparator configured to compare identifiers associated with data storage elements of one or more partitions with the identifier associated with the required data item, wherein any partitions in the subset of partitions are excluded from the test group of partitions. The tag preferably comprises a part of the most significant portion of the memory addresses; and the predictor preferably compares a partition hash value derived from the identifiers (e.g. tags) associated with the storage elements of that partition with a hash value derived from an identifier associated with the required data item.