In some examples, a system performs data deduplication using a deduplication fingerprint index in a hash data structure comprising a plurality of blocks, wherein the hash data structure is stored in persistent storage, and a block of the plurality of blocks comprises fingerprints computed based on content of respective data units. The system uses an indirect block in a memory to access a given block of the plurality of blocks in the hash data structure, the indirect block containing references to blocks of the hash data structure containing the deduplication fingerprint index, and the references indicating storage locations of the plurality of blocks in the persistent storage.