1. A computer program product for performing deduplication for a storage, the computer program product comprising a non-transitory computer readable storage having computer readable program code embodied therein that executes to perform operations, the operations comprising: maintaining an index, comprising a deduplication index, of chunk signatures calculated from chunks of data in data objects in the storage, wherein each index entry includes at least one of the chunk signatures and a reference to the chunk of data from which the signature was calculated; selecting entries in the index to merge, comprising merged selected entries, referencing consecutive of the chunks of data in the storage; performing a merge operation on the chunk signatures in the merged selected entries to calculate a merged signature; adding an entry to the index, wherein the added entry comprises the merged signature and a reference to the consecutive chunks in the storage referenced by the merged selected entries; removing the merged selected entries used to calculate the merged signature from the index; and using the index of the signatures in deduplication operations when adding data objects to the storage.