IMAP-based 檔案系統之設計與實作

Abstract

現今郵件服務提供越來越大的郵件儲存空間，再加上其支援更有效率與便於管理的郵件存取協定，使得我們可以在伺服器上規劃分類所擁有的電子信件，並能在不同地方使用任何裝置，輕鬆存取相同帳號的信件。 本論文提出我們研製之PamiFS檔案系統。PamiFS檔案系統是將具有IMAP(Internet Message Access Protocol)連線功能的郵件伺服器，設計掛載到主機的檔案系統上，使得郵件伺服器所提供的信件儲存空間，變成個人的網路檔案硬碟，提供私人檔案儲存與群體檔案分享之運用。 PamiFS檔案系統是在使用者空間運作的程式。在與Linux的檔案系統掛載上，是藉由向FUSE系統註冊反向呼叫函數，再經由FUSE系統，透過虛擬檔案系統系統(VFS)，掛載到Linux作業系統中。透過這些反向呼叫函數，來實行PamiFS檔案系統的操作行為。 PamiFS檔案系統，在檔案的存取方面，使用IMAP協定，實現從郵件伺服器下載與查詢的動作，使用SMTP協定，實現對郵件伺服器上傳的動作。在系統驗證方面，我們利用Mail2000電子信箱為例，實行PamiFS檔案系統的操作與測試。實驗結果顯示，在離峰時間上操作時間有較穩定的反應時間。在尖峰的時間操作，因為受到電子郵件伺服器忙於處理信件之影響，檔案讀寫效率反應較差。

Mail storage spaces provided by e-email service providers become increasingly large. In addition, more efficient e-mail mail protocols are supported, allowing users to manage their e-mail messages more efficiently and easier. The main goal of this study is to design a file system, which is called the PamiFS. PamiFS stores the user files in the e-mail storage spaces and provides a usual file system interface to the users. With PamiFS, an e-mail storage can be translated into a local storage for storing user files. Currently, PamiFS supports IMAP (Internet Message Access Protocol) based e-mail servers. Users can store their files into their own PamiFS file systems or share those files with others. PamiFS is a FUSE-based user space file system. Currently, PamiFS runs on Linux. PamiFS uses the query function of the IMAP protocol to filter information or download attached files, and it uses the SMTP protocol for uploading files. The functionality of PamiFS was verified on the Mail2000 e-mail system. A more stable performance was observed when the email traffic is not high (i.e., off-peak time). When the email traffic is high (i.e., peak time), a degraded performance and a larger performance variance were observed.