Abstract: The methods of the invention of storing a data item and the associated method of repair of a failed storage device allow exact repair of the data lost by a failed storage device in a distributed data storage system. As repaired data is exactly identical to lost data, this simplifies data integrity checking, which is appealing for distributed data storage systems that require a high level of data security. The methods and devices of the invention use erasure correcting codes that are optimized at the MBCR point such that they minimize both storage size required to store a data item and repair bandwidth required for data- and message exchange between the devices of the distributed storage system in case of repair.