Functional-repair-by-transfer regenerating codes

In a distributed storage system, a data file is distributed to several storage nodes, such that the original file can be decoded from any subset of the storage nodes of size larger than or equal to a certain threshold. Upon the failure of a storage node, we would like to regenerate it with minimal amount of data transmissions from the surviving nodes to the new node. This performance metric is called the repair-bandwidth. Another performance metric is the disk input/output (I/O) cost, which measures the number of bits a storage node needs to read out from its memory in order to repair the failed node. In this paper, we give examples of linear regenerating codes with minimal disk I/O cost and repair-bandwidth, without any linear mixing in the helping storage nodes.