即時多媒體資訊系統其資料配置策略之效益評估

Abstract

由於多媒體資料所需要的儲存空間相當龐大，而且資料的存取又多有 時間上的要求，因此多媒體資訊系統的效能是它必須克服的重要問題。其 中，多媒體資料的儲存管理雖然複雜，但是對多媒體資料系統來說卻是非 常基本的。有效且容易使用的儲存管理方法及工具對未來多媒體資訊系統 的發展是絕對需要的。 我們研究的主要目的是在探討對於一個必須滿 足即時要求的多媒體資訊系統來說，資料配置策略所造成的影響。我們提 出數種資料配置的方法，並設計了即時多媒體資訊系統的模擬環境，以此 模擬環境下的實驗結果來評估這些方法的效能。 實驗結果顯示：資料 配置策略對系統的效能影響很大，尤其在系統負載量大、媒體存取頻率偏 差、CPU及磁碟速度較快的情況下。對資料配置策略的考量，我們提出以 下兩項建議。一是當媒體存取頻率偏差時，應考慮各種媒體物件的平均存 取頻率；二是在系統配置有較高速的CPU及磁碟時，應將各種媒體物件的 平均存取時間考慮進來，以改善即時多媒體資訊系統的效能。 A Multimedia Information System (MMIS) has to address difficult performance problems due to the massive volume of multimedia as well as the real-time requirements. Multimedia data storage management is complex but essential for the development of a MMIS. Effective and easy-to-use design methods and tools for multimedia data storage management are an absolute necessity for further developments of such systems. Our research goal is to investigate the effects of data allocation strategies on meeting real-time requirements for MMIS. We propose various data allocation strategies and evaluate their performance through simulation experiments. The experimental results show that data allocation strategies have significant impact on real-time response of a MMIS. The main factors dominating a real-time MMIS's performance are system load, access frequency, CPU and disk speed. We provide two suggestions for using proper data allocation strategies to improve the performance of a MMIS. The first one is that the access frequency of each medium object should be considered for skewed access frequency; the second one is that the access time of each medium object should be taken into account under higher-speed CPU and disks.