將重要資料透過網際網路備份到遠端的資料中心逐漸成為一種趨勢，但是利用網路進行資料備份的過程相當漫長且需人為介入，干擾使用者正常工作的時間。連續資料保護（CDP，Continuous Data Protection）技術是以安裝在電腦系統的中介程式監督檔案動作，只將重要資料的副本自動複製到其他磁碟裝置或透過網路傳送到遠端的儲存服務，因而可免除使用者操作的困擾和大量資料的網路傳輸。現今大部分的行動式電腦均內建無線網路，並普遍利用無線網路將資料傳送到資料中心。然而在無線網路的環境，連續資料保護系統在將歷程資料傳輸到資料中心時，會因連線頻寬不足、封包延遲時間過久、或是錯誤機率太高，而需在系統底層不斷進行重新傳送，造成電腦系統長時間等待資料完成而影響運作效能，因此連續資料保護技術目前仍不適合直接在無線網路上使用。本研究提出在作業系統啟動之前備份和還原行動電腦磁碟資料的方法，以檢查歷程資料累積的資料量為參考點，當資料量超過一定的門檻值，系統自動開啟無線網路並和網路儲存服務建立連線，隨即將資料複製到網路儲存伺服器，以降低資料損毀的風險成本。我們採用幾種不同的資料傳輸技術和無線網路連接架構評估系統的效能，從結果中可看出支援多重連線和非同步傳輸功能的iSCSI通訊技術作為無線網路資料傳輸的骨幹，不僅具有較佳的傳輸效率同時也較能抵抗高延遲環境的干擾。 Data backup via internet has become a trend, but the process is time-consuming and laboring, which interferes users’ normal working. Continuous Data Protection (CDP) monitors the data process with an agent program embedded in computer systems. It automatically copies the critical data to other drives or transmits data to the remote data center via internet, which successfully prevents operational troubles and enormous data transmission. Nowadays most portable computers have a built-in wireless network adapter, which is widely used to backup important data to the remote data center. Nevertheless, when transmitting data over a wireless network, CDP encounters problems of losing and repeating transmission for insufficient bandwidth, packet latency or high packet error rate. The long-time delay of computer systems seriously influences the overall efficiency, so CDP is so far not suitable for wireless networking environment. This study proposes a method to backup and restore CDP or critical data in portable computers before operating systems start. Our method begins by checking the accumulated log data and when the data reaches a certain threshold value, the system automatically turns on wireless network and connects to the remote data center. By copying the data to the data center promptly, the system could lower down the risk cost of data corruption. Using the wireless network evaluation system, we compared the performance of several different data transmission techniques. The results show that iSCSI (internet Small Computer System Interface), supporting multiple connections and asynchronous IO, can be a good transmission backbone of wireless networks because of its better transmission efficiency and greater tolerance of high network latency.
