一個有效的分散式視訊伺服器系統之工作排程方法

Abstract

由於電腦與多媒體技術的進步，隨選視訊服務已被廣泛應用並影響人們的生活。然而，隨著使用者對服務要求的提升，單一伺服器的架構缺乏擴充性與伺服器層次的系統容錯功能。為了解決這些問題，許多研究提出了多重伺服器的架構。 在這篇論文中，我們將提出一個具擴充性的視訊伺服器系統。我們的架構不僅採用分散式儲存伺服器，同時也採用分散式使用者管理機制。在多重伺服器架構中，廣泛的輪置技術(Wide Striping)是一個具成本效益的資料排列方法。但是，使用者不均衡的存取仍會造成系統效能低落。因此，我們設計了一個工作排程方法，利用控制使用者點播影片的啟動時間來發掘系統未使用的資源。使用我們的方法，在不同的模式下，可獲得最小延遲時間或者較佳的系統負載之平衡。從模擬結果可知，我們的方法可有效地降低系統負載不均衡的情況，進而提昇系統的效能。詳細的設計原理與效能評估將在論文以後的章節中一一介紹。

Due to the advances in computer and multimedia techniques, the applications of video-on-demand are visible and influence people's life worldwide. However, with the growth of service demand, the single-server architecture is limited by its scalability and server-level fault-tolerance. Recently, several multi-server architectures are proposed to alleviate such problems. In this thesis, we will propose a scalable architecture for video server management system. Our architecture employs not only distributed storage servers but also distributed subscriber management. Wide striping technique is a cost-effective data placement in multi-server architecture. However, the unpredictable access skew from users results in performance degradation. Therefore we design a new scheduling policy to fully utilize the potential bandwidth of wide striping by controlling the startup time of each request. With different modes of our policy, we can benefit from minimum delay or load balance. According to our simulation results, our policy efficiently alleviates load imbalance and thus improves system performance. The detailed information about design principles and performance evaluations will be described in the literature.