由於現今數據量呈現爆炸性的增長，所以現有的儲存技術已開始不堪使用，故在過去幾年中已有學者提出了多種能提高相同面積下儲存密度的技術。其中以疊瓦式儲存技術（SMR）被認為是當前能最快面向使用者的技術，因其基於垂直儲存技術的硬碟，故在不大幅度變動架構下其為最有希望的選擇。而雖然SMR儲存技術帶來了低成本的高容量儲存設備，但因其結構的調整導致了SMR硬碟的隨機存取性能嚴重低弱。而為了提高SMR的存取性能，固態混合硬碟（SSHD）是其中一種的解決方案，但是若再大型數據管理系統中應用了基於SMR的SSHD時，由於其需要一直維護索引與資料的一致性，故會導致其存取性能嚴重下降。更具體地說，由於SSHD在更新時所執行 讀-合併-寫 的操作或是硬碟GC行為，均會讓索引和數據因異地寫入(Out-of-place write)的關係導致嚴重的寫入放大。基於這樣的原因，本論文提出了一解決方案，於疊瓦式技術之混合硬碟上對於鍵值儲存應用啟用B+-Tree資料管理設計，即XsB+-tree。而本論文是首個討論基於疊瓦式技術之混合硬碟上的鍵值存儲的整體解決方案。而根據實驗結果，XsB+-tree平均可以將縮短80％的存取時間，並延長SSD 19％的使用壽命。

Owing to the explosive growth of data volume, high areal density storage technologies have been proposed in the past few years. Among them, shingled magnetic recording (SMR) has been regarded as the most promising candidate to replace current conventional hard disk drive based on the perpendicular magnetic recording technology. However, SMR technology not only brings large capacity storage devices but also results in terrible random access performance. For increasing the random access performance of SMR, solid-state hybrid drive (SSHD) seems a possible solution in storage system development. Nevertheless, when an SMR-based SSHD is adopted to a large-scale data management system, a severe performance degeneration will happen because an indexing scheme for access efficiency always maintains data in the large-scale data management system. More specifically, jointly managing indexing keys and data values on an SSHD drive will result in the massive amount of write amplification because of read-merge-write operations and garbage collection processes. Based on such motivations, this work proposed a total solution, namely XsB+-tree, to establish a high-performance B+-tree-based data management scheme for key-value store systems. To the best of our knowledge, this work is the first work to discuss the total solution for the key-value store over an SMR-based SSHD. According to our experimental results, XsB+-tree can improve the access time by 80% on average and prolong the lifetime of SSD up to 19%.

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