本論文提出一個稱為Reef的超檔案系統(Hyper File System)。Reef 結合軟體定義網路(Software-Defined Networking, SDN)及分散式檔案系統(Distributed File System, DFS) 技術。使用軟體定義網路的控制器(Controller)集中式管理網路通信量，可以更有效率的分配網路資源解決網路壅塞、降低延遲時間及減少頻寬消耗;使用分散式檔案系統當作儲存空間，則具有高度的可擴展性，營運商可以根據需求增加或減少儲存資源，使得檔案系統的使用更佳靈活。Reef也整合糾刪碼(Erasure code, EC)提高資料可靠性。糾刪碼是一種數據容錯方法，它將數據分割成不同片段，將其擴展、編碼，並存儲在不同的位置。相比多副本複製容錯方法而言，糾刪碼能夠以更小的數據冗餘獲得更高數據可靠性。本論文也提出Residual-Network Multiple Shortest Path (RNMSP)演算法找出路徑以到達平均端點至端點延遲(Average end to end delay)最低的儲存節點，並將經過糾刪編碼後的檔案存在各個節點，達到異地備源的功能。本論文並針對RNMSP演算法及其他儲存節點路徑尋找演算法在不同網路拓樸上進行模擬，以比較其執行時間及平均端點至端點延遲。;In this study, we propose a hyper file system, named Reef, which is a combination of the technologies of Software Defined Networking (SDN) and the Distributed File System (DFS). Reef uses the SDN controller to manage network traffic in a centralized way so that the network resources can be allocated more efficiently to reduce network latency, congestion, and bandwidth consumption. Furthermore, Reef uses DFS storage nodes to store data to keep high scalability; operators can increase or decrease storage resources dynamically according to users demands, leading to high utilization of the file system. Reef also integrates the erasure code (EC) to improve data reliability. The EC is a method to make data fault-tolerant; it divides data into different fragments, which are encoded with redundancy to be stored across a set of different locations. Compared with the traditional multi-replica method to make data fault-tolerant, the EC can utilize smaller data redundancy for higher data reliability. We also propose the Residual-Network Multiple Shortest Path (RNMSP) algorithm to find paths to the storage nodes minimizing the average end to end delay for storing EC-encoded data blocks. We simulate the RNMSP algorithm and other related storage node path-finding algorithms under different network topologies for comparing algorithms in terms of the execution time and the average end to end delay.
