隨著高速網路的發展，人們開始使用網路將網路上的許多儲存裝置串聯成一個超大型的儲存系統。目前分散式檔案系統也已逐漸成為人類社會中不可或缺的一部分，並且開始影響著人們的生活。除此之外，近年來人們開始提出了以物件為基礎的儲存概念。它強調在儲存系統中的任何資訊以及資料皆應被視為是一種物件，而檔案系統不需要去了解這些儲存上的細節，就可以透過這些物件來管理這些檔案的資料。而目前已有許多人認為以物件為基礎的儲存概念將會是未來的一種主流，因此已有許多人將以物件為基礎的儲存概念跟分散式檔案系統互相結合在一起，並且提出一些以物件為基礎的分散式檔案系統。
隨著時間的發展，現代化的分散式檔案系統已具備有高擴充性、高可靠度、以及高效率等特質。然而截至目前為止，目前的檔案系統尚未針對資料插入以及資料刪除做有效率的處理。倘若一個檔案系統能支援資料插入及刪除的話，將能大大地省去我們修改檔案內容的時間。因此，我們提出了Wofs，一個專門針對資料插入以及資料刪除、並且以物件為基礎的分散式檔案系統。Wofs將一個檔案切割成好幾塊物件，並將這些物件儲存到網路上的遠端儲存裝置裡，並且使用一種特別的樹狀結構來管理這些物件的資訊。使用這樣的設計便能讓Wofs能夠穩定且有效率地支援資料插入及刪除的動作。除此之外，Wofs採用以物件為單位的locking策略來避免資料不一致性的問題，並且減少locking對效能上的損失，如此一來Wofs將會變得更有效率。而根據本論文最後的效能測試結果，我們可以知道Wofs在資料插入及刪除之下的確能有穩定且良好的效能，這顯示了Wofs有效率且程式簡潔有力的特質。

With the development of high-speed networks, people begin to use networks to combine all storage devices to form a huge distributed file system. Now distributed network file systems become more and more important and influential. Besides, in recent years, the concept of object-based storage has been brought up. It emphasizes all things in disks should be seen as objects, and file systems can manage all file data via these objects ignoring the storage details. Now many people believe object-based storage will become a main trend in the next generation of hard drives. With this, people begin to combine distributed network file systems with the concept of object-based storage. Now, more and more object-based distributed network file systems have been presented.
As time goes by, most distributed file systems become more and more scalable, reliable and high-performance. But until now, there are still no file systems supporting fast arbitrary data insertion and truncation which reduce the time for file modification significantly. So we present Wofs, an object-based distributed network file system with support for fast arbitrary data insertion and truncation. Wofs splits a file into many small objects, stores these objects in remote file servers, and uses a special B+tree to manage the metadata of these objects. With this design, Wofs can provide good and stable performance for data insertion and truncation. Besides, Wofs uses the object-range locking policy to avoid data incoherence and improve the performance. At the final part of this thesis, the performance evaluations show Wofs has stable performance and high throughput on data insertion and truncation, which implies that Wofs is efficient and neat.

[1] Myricom, “Myrinet”, http://www.myri.com/.
[2] S. Ghemawat, H. Gobioff, and ST. Leung, “The Google File System”, ACM SIGOPS Operating Systems Review, vol. 37, no. 5, pp. 29–43, Dec. 2003.
[3] M. Mesnier, G. R. Ganger, and E. Riedel, ”Object-Based Storage”, IEEE Communications Magazine, vol. 41, no. 8, pp. 84–90, Aug. 2003.
[4] S. A. Weil, S. A. Brandt, E. L. Miller, D. D. E. Long, and C. Maltzahn, “Ceph: A Scalable, High-Performance Distributed File System”, in Proceedings of the 7th Symposium on Operating Systems Design and Implementation (OSDI), pp. 307–320, 2006.
[5] O. Rodeh, and A. Teperman, “zFS - A Scalable Distributed File System Using Object Disks”, in Proceedings of the 20th IEEE / 11th NASA Goddard Conference on Mass Storage Systems and Technologies, pp. 207–218, Apr. 2003.
[6] P. H. Carns, W. B. Ligon III, R. B. Ross, and R. Thakur, “PVFS: A Parallel File System for Linux Clusters”, in Proceedings of the 4th Annual Linux Showcase and Conference, pp. 317–327, 2000.
[7] F. Schmuck and R. Haskin, “GPFS: A shared-disk file system for large computing clusters”, in Proceedings of the 2002 Conference on File and Storage Technologies (FAST), pp. 231–244, Jan. 2002.
[8] R. Bayer and E. McCreight, “Organization and maintenance of large ordered indexes”, Acta Informatica, vol. 1, pp. 173–189, 1972.
[9] D. Comer, “The Ubiquitous B-Tree”, ACM Computing Surveys (CSUR), vol. 11, no. 2, pp. 121–137, Jun. 1979.
[10] M. J. Carey, D. J. DeWitt, J. E. Richardson, E. J. Shekita, “Object and file management in the EXODUS extensible database system”, in Proceedings of the 12th International Conference on Very Large Data Bases, pp. 91–100, Aug. 1986.
[11] A. Sweeney, D. Doucette, W. Hu, C. Anderson, M. Nishimoto, and G. Peck, “Scalability in the XFS File System”, in Proceedings of the USENIX 1996 Technical Conference, pp. 1–14, 1996.
[12] R. O. Weber, “SCSI object-based storage device commands (OSD-2)”, Technical Report, INCITS Technical Committee T10/1729-D, Jan. 2007.
[13] A. Azagury, V. Dreizin, M. Factor, E. Henis, D. Naor, N. Rinetzky, O. Rodeh, J. Satran, A. Tavory, and L. Yerushalmi, “Towards an object store”, in Proceedings of the 20th IEEE / 11th NASA Goddard Conference on Mass Storage Systems and Technologies, pp. 165–176, Apr. 2003.
[14] E. V. Hensbergen and R. Minnich, “Grave robbers from outer space: Using 9p2000 under linux”, in Proceedings of Freenix Annual Conference, pp. 83–94, 2005.
[15] “v9fs”, http://swik.net/v9fs.
[16] “spfs”, http://sourceforge.net/projects/npfs.
[17] R. Pike, D. Presotto, K. Thompson, and H. Trickey, “Plan 9 from Bell Labs”, in Proceedings of the Summer 1990 UKUUG Conference, pp. 1–9, Jul. 1990.
[18] D. Presotto, R. Pike, K. Thompson, and H. Trickey, “Plan 9: A distributed system”, in Proceedings of Spring 1991 EurOpen, pp. 43–50, May 1991.