Beyond the MDS bound in distributed cloud storage

Distributed storage plays a crucial role in the current cloud computing framework. After the theoretical bound for distributed storage was derived by the pioneer work of the regenerating code, Reed-Solomon code based regenerating codes were developed. The RS code based minimum storage regeneration code (RS-MSR) and the RS code based minimum bandwidth regeneration code (RS-MBR) can achieve the theoretical bounds on the MSR point and the MBR point respectively in code regeneration. They can also maintain the MDS property in code reconstruction. However, in the hostile network where the storage nodes can be compromised and the packets can be tampered with, the storage capacity of the network can be significantly affected. In this paper, we propose a Hermitian code based regenerating (H-MSR) code. We first prove that this code can achieve the theoretical MSR bound. We then propose data regeneration and reconstruction algorithms for the H-MSR code in both error-free network and hostile network. Theoretical evaluation shows that our proposed schemes can detect the erroneous decodings and correct more errors in the hostile network than the RS-MSR code with the same code rate. Our analysis also demonstrates that the proposed H-MSR code has a lower complexity than the RS-MSR code in both code regeneration and code reconstruction.