近幾年來，高速網路發展迅速，像Gigabit，Myrinet以及Infiniband的傳輸速度已經逼近匯流排的傳輸速度。由於磁碟機的讀取速度相對於高速網路實在太慢，所以我們可以經由高速網路讀取遠端機器的快取檔案，這樣的讀取速度遠遠快於原本的磁碟機讀取速度。在這篇論文中，我們提出並且實做了一個通用檔案快取(Universal File Cache or UFC)，它可以完整的利用並且整合所有的記憶體資源在一個用高速網路連接起來的分散式系統中。對應用軟體而言，通用檔案快取提供了一個大型並且唯讀的快取空間。任何應用軟體可透過通用檔案快取系統所提供的應用程式介面去分享檔案進而避免檔案在快去中重複的現象。為了使我們的系統容易延伸並且擴展到異質性的分散式系統中，我們將通用檔案快取實做成一個中介軟體，它包含了兩個主要的元件，cache driver和communication daemon。為了能夠快速的在通用檔案快取系統中取得檔案，我們設計了新穎並且有效率的尋找檔案演算法(file lookup algorithm)。另外還有migration和replication演算法來幫助系統管理快取檔案。在實驗中，通用檔案快取大大的增進了web server的效能，避免掉了大部分的磁碟機讀取，成功了提昇了使用通用檔案快取的應用軟體的效能。

The speed of data transmission over high-speed networks such as Gigabit, Myrinet, and Infiniband has come close to that of the system bus in modern computers. Due to the relatively low speed of disk access, reading a cached file in a remote machine connected through a high-speed network is significantly faster than reading the file from a local disk. In this paper, we propose and implement a universal file cache called UFC that fully utilizes and integrates all memory resources in a high-speed distributed system for comprehensive file caching. UFC presents to all applications a single large-scaled read-only file cache. Through a set of publicly-accessed interfaces, every application can share cached files in UFC and avoid multiple caching. To be easily extended and deployed in a heterogeneous distributed system where machines are installed with different operating systems and connected with different communication media, we develop UFC as a middleware consisting of add-on cache drivers and communication daemons built on top of the well-supported BSD socket library. To efficiently locate a file in UFC, we present a novel file lookup algorithm and a set of cache management algorithms dealing with file migrations and replications. We illustrate the performance impact of UFC by a web server that accesses a large file set. The experimental results show that, by caching files in UFC and avoiding expensive disk access, we significantly improve the performance of the web server.
Keywords: universal file cache, heterogeneous distributed systems, operating systems, clustered systems

[1] T. Anderson, D. Culler, and D. Patterson. A Case for NOW
(Networks of Workstations). In IEEE Micro, 15(1):54-64,1995.

[2] Thomas Anderson, Michael Dahlin, Jeanna Neefe, David Patterson, Drew Roselli, and Randolph Wang. Serverless network file systems. In Proceedings of the 15th Symposium on Operating System Principles. ACM, pages 109{126, Copper Mountain Resort, Colorado, December 1995.

[3] Marshall Bern, Daniel Greene, and Arvind Raghunathan. Online algorithms for cache sharing. In Proceedings of the twenty-fifth annual ACM symposium on Theory of computing, pages 422-430. ACM Press, 1993.

[4] B. Bloom. Space/time trade-offs in hash coding with allowable errors. Communications of the ACM, vol. 13, no. 7, pages 422-426, July 1970.

[5] Anawat Chankhunthod, Peter B. Danzig, Chuck Neerdaels,
Michael F. Schwartz, and Kurt J. Worrell. A hierarchical in-ternet object cache. In USENIX Annual Technical Conference,
pages 153-164, 1996.

[6] G. Chen, C.L. Wang, and F.C.M. Lau. Building a scalable web server with global object space support on heterogeneous clusters. In Proceedings of IEEE International Conference on Cluster Computing, 2001.

[7] T. Cortes, S. Girona, and J. Labarta. PACA: A Distributed File System Cache for Parallel Machines. Technical Report Technical Report UPC-DAC-1995-20, Departament d'Arquitectura de computadors, Universitat Politecnica de Catalunya (UPC), June 15 1995.

[8] Michael Dahlin, Randolph Wang, Thomas E. Anderson, and
David A. Patterson. Cooperative caching: Using remote client
memory to improve file system performance. In Operating Sys-
tems Design and Implementation, pages 267-280, 1994.

[9] Li Fan, Pei Cao, Jussara Almeida, and Andrei Z. Broder. Summary cache: a scalable wide-area Web cache sharing protocol. IEEE/ACM Transactions on Networking, 8(3):281-293, 2000.

[10] Michael J. Feeley, William E. Morgan, Frederic H. Pighin, Anna R. Karlin, Henry M. Levy, and Chandramohan A.
Thekkath. Implementing global memory management in a work-
station cluster. In Symposium on Operating Systems Principles, pages 201-212, 1995.

[11] Thu D. Nguyen Francisco Matias Cuenca-Acuna. Cooperative caching middleware for cluster-based servers. In Tenth IEEE International Symposium on High Performance Distributed Computing (HPDC-10). IEEE Press, August 2001.

[12] Syam Gadde, Jeff Chase, and Michael Rabinovich. A taste of crispy Squid. In Proceedings of the Workshop on Internet Server Performance (WISP'98), 1998.

[13] Zornitza Genova and Kenneth J. Christensen. Challenges in URL switching for implementing globally distributed web sites. In ICPP Workshop, pages 89-94, 2000.

[14] John H. Hartman and John K. Ousterhout. The Zebra striped network file system. In Proceedings of the 14th ACM Symposium on Operating Systems Principles, pages 29-43, 1993.

[15] John H. Howard, Michale L. Kazar, Sherri G. Menees, David A. Nichols, M. Satyanarayanan, Robert N. Sidebotham, and Michael J. West. Scale and performance in a distributed file system. ACM Transactions on Computer Systems, 6:51-81, 1988.

[16] ICP working group. National Lab for Apllied Network Research. http://www.ircache.net/.

[17] InfiniBand Trade Association.
http://www.infinibandta.org/.

[18] Information and Communication Technologies at CSIRO Australia. http://www.ict.csiro.au/gigabit/gigabitradio.htm.

[19] David Karger, Eric Lehman, Tom Leighton, Mathhew Levine, Daniel Lewin, and Rina Panigrahy. Consistent hashing and random trees: Distributed caching protocols for relieving hot spots on the world wide web. In ACM Symposium on Theory of Computing, pages 654-663, may 1997.

[20] Evangelos P. Markatos and George Dramitinos. Implementation of a reliable remote memory pager. In USENIX Annual Technical Conference, pages 177-190, 1996.

[21] Myrinet. http://www.myrinet.com/.

[22] NTT Microsystem Integration Laboratories. Development of Large-Scale Integrated Optical Switched Based on Silica Waveguide.http://www.ntt.co.jp/saiyo/e/rd/review/pdf/ct07.pdf.

[23] Sean C. Rhea and John Kubiatowicz. Probabilistic location and routing. In Proceedings of INFOCOM 2002.

[24] Prasenjit Sarkar and John H. Hartman. Hint-based cooperative caching. ACM Transactions on Computer Systems, 18(4):387-419, 2000.

[25] Bill N. Schilit and Dan Duchamp. Adaptive remote paging for mobile computers. Technical Report CUCS-004-91, Department of Computer Science, Columbia University, 1991.

[26] Standard Performance Evaluation Corporation.
the specweb99 benchmark. http://www.spec. org/osg/web99/.

[27] Chandramohan A. Thekkath, Timothy Mann, and Edward K.
Lee. Frangipani: A scalable distributed file system. In Symposium on Operating Systems Principles, pages 224-237, 1997.

[28] Jeffery Westbrook. Randomized algorithms for multiprocessor page migration. In DIMACS Series in Discrete Mathematics and Theoretical Computer Science, volume 7, pages 135-150, 1992.