基於相變化記憶體檔案系統的有效率磨損機制

Abstract

近年來，隨著非揮發性記憶體研究上的突破，下一個世代的記憶體技術也漸漸誕生而且對現有的電腦架構產生很大的衝擊，其中，以相變化料為主的相變化記憶體(PCM)是最具有潛力的候選裝置，其本身具有非揮發性，位元組定址能力，以及接近動態隨機存取記憶體的速度等優勢，因而在儲存系統上非常具有優勢。利用相變化記憶體為主的儲存系統可以克服斷電等重要的可靠度問題，而且還能拉近儲存系統和記憶體系統間速度上的差距。然而，傳統的檔案系統的設計並能未針對相變化記憶體做最佳化，尤其是檔案系統本身的中介資料，其具有大量且集中寫入的特性會造成相變化記憶體因為過度寫入而毀壞。在這篇論文中，我們提出了一個基於相變化記憶體的儲存系統架構，來探索傳統檔案系統在相變化記憶體上的應用。在這個架構下，我們主要是延伸了傳統的檔案系統架構，使其能在有限度地修改下，獲得相變化記憶體所帶來的快速存取和保護中介資料的目的，此外我們實踐了一個以行進策略為主的平均磨損機制，透過可調整的視窗來適應不同的存取行為，並且擺脫傳統在執行平均磨損時需要大量搜尋的問題。在實驗的結果顯示，傳統的檔案系統在我們的架構下性能可以獲得有效的提升，而且相變化記憶體的壽命問題透過行進策略為主的機制可以有效的解決。

In recent years, with the breakthrough of processing of non-volatile memories, the next generation memories have emerged and have a big impact of the existing computer architectures. Among of those memories, phase change memory(PCM) is the most potential candidate device for next generation memories. Non-volatility, byte-addressability and near DRAM speed make it a proper character for storage systems. A PCM-based storage system could overcome important reliability issues such as power failure and reduce the speed gap between storage and memory. However, the traditional file systems are not optimize for PCM, in particular, the metadata management of the file systems make the problem worse, the high locality of writes make the PCM wore out fast. In this paper, we propose a reliable PCM-based file system, which is extended to the traditional file systems with limited modifications, to explore the applications for traditional file systems on PCM. Besides, we also propose a marching-based strategy of wear-leveling, which contains an adaptive marching-window for different workloads, to enhance the endurance of PCM with the limited searching overheads. The experiment results shows that the proposed architecture and the marching window-based wear-leveling could significantly improve the performance of the file systems and the endurance of PCM.