藉由減少I/O以及磁碟資料區塊不連續現象以增進POP3伺服器效能

Abstract

隨著近年來網路的發達程度，越來越多人使用電子郵件，而因為網路速度越來越快，所以收取信件的速度取決於POP3伺服器的效能，所以改善POP3伺服器效能可望有效增進收取郵件速度。 根據我們觀察實際郵件伺服器得知，當信件檔案變大的時候在磁碟上的分布往往變的破碎，同時根據我們的先期實驗發現，同樣大小的信件檔案根據不同的連續程度存取的速度也有相當大的差距。所以我們提出一個機制，此機制可以做到在刪除信件的過程中，即時的進行減少碎裂部份的功能，同時又可以減輕原本伺服器在刪除信件時所需要耗費的大量資源。由實驗結果可顯示我們所提出之機制可確實達到所以我們所提出之改善。

Email is one of the most widely-used network services in our daily life. Because the network speed is more and more fast, clients are more sensitive about the performance of POP3 server when retrieving mails. So we can fasten the duration of retrieving mails by improving the performance of POP3 servers. According to our prior observation on a real POP3 server, we find that when the mail folders grow larger, they are more fragmented on disk. And we find that it takes more time to read a more fragmented mail folder. In this thesis, we proposed a mechanism to do defragmentation during mail deletions, and we can mitigate the large amount of disk I/O and memory access caused by mail deletion. As shown in experimental result our mechanism can do defragmentation more effectively with lower overhead than original mechanism.