Theoretically total bandwidth conserving locality in Distributed Storage System

Distributed storage systems provide fast and reliable access to data by intro- ducing redundancy for stored les. The most common approach of adding re- dundant information is by repetition and erasure codes. Two main processes in a distributed storage system are reconstruction of original le and regenerat- ing a new node. These two processes require bandwidth, which are termed as reconstruction-bandwidth and repair-bandwidth. The current literature treat- s these two processes separately. That is, there are methods to reduce the reconstructing bandwidth without considering the repair-bandwidth, and also there are methods to reduce the repair-bandwidth. We study these two pro- cesses together and try to jointly minimize the reconstruction-bandwidth and repair-bandwidth. We observe a method that has the minimum reconstruction- bandwidth might have large amount of repair-bandwidth and vice versa. We propose codes which minimizes the sum of the repair-bandwidth and reconstruction- bandwidth. The main contribution of this thesis is nding an value of repair locality r (number of nodes connected during node repair) and devising two coding meth- ods in which total bandwidth approximates to be half reduced compared with MSR and MBR when k ! 1 under the condition that 1 6 r 6 k