The efficiency of data de-duplication may be improved by storing related file data in a single container, or in multiple linked containers, of a history. Additionally, the efficiency of data de-duplication may be improved when shorter hash tables are used to reference historical data in a history. Shorter hash tables may be achieved by storing fewer than all the hash values obtained for a given amount of historical data. Further, the efficiency of data de-duplication may be improved by comparing related incoming file data with historical data from a container without hashing/chunking the remaining file data upon matching an earlier chunk of the incoming file data to the container.