Overview

The Modify-on-Access (Mona) file system is an active file system that cooperates with processes to accomplish tasks. Mona uses modular streaming operations, transformations, to transparently perform actions on behalf of a user process during a read or write. As a result, the Mona file system extends the capabilities of conventional file systems which passively transfer data through streams between kernel buffers and secondary storage.

A transformation, the basic unit of computation performed by the Mona file system, is an arbitrary operation on a stream of data. The file system transforms data when it is accessed. On a read, the file system applies transformations to data before presenting it to a user process. Similarly, it applies transformations to data before writing it to disk. Compression is a simple and obvious use of transformations. On input, the read transformation decompresses data as it is read from the file and on output, the write transformation compresses data. As a result, the Mona file system provides transparently compressed files which hide details of the compression from users who access a compressed file as though it were a normal file.

The Mona file system supports kernel-resident and user-defined extensions, enabling it to be efficient and flexible. Common, trusted operations reside within kernel transformations that execute quickly and incur minimal overhead relative to a base file system. A kernel-resident identity transformation (functionally equivalent to the base file system) adds an overhead of 3--5\%. Arbitrary user-defined operations execute in user space, providing extensibility without endangering system security.

The Mona file system is the first component of a suite of system software designed for a collaborative memory system in which the memory system and intelligent peripheral devices collaborate with a host processor to accomplish tasks. Related projects include a Mona virtual memory system and a Mona peripheral device.

Future work

Availability

Additional Information

Journal Articles:

• H. Richard Kendall, Vincent W. Freeh, Paul W. Schermerhorn, Peter W. Rijks, and Robert J. Minerick. Streaming extensibility in the modify-on-access file system, To appear in J. of Systems and Software, 2002.
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• H. Richard Kendall and Vincent W. Freeh. The design and implementation of the exported procedure call, Software--Practice and Experience, 32(1):83-98, January 2002.
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Conference and Workshop Proceedings:

• Paul W. Schermerhorn, Robert J. Minerick, Peter W. Rijks, and Vincent W. Freeh. User-level extensibility in the mona file system, In proceedings of Freenix Conference, pp. 173-184 , Boston, MA, June 2001.
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• H. Richard Kendall and Vincent W. Freeh. Magi: A System Software Model for Intelligent Devices In The Second International Workshop on Compiler and Architecture Support for Embedded Systems, Washington, D.C., October, 1999.
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• Richard Kendall and Vincent Freeh. The Modify-on-Access File System: An Extensible Linux File System Proc. of the International Linux Conference, San Jose, CA, March 2-4, 1999.
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Technical Reports:

• Robert J. Minerick, Paul W. Schermerhorn and Vincent W. Freeh. A File System Interface to the Internet, Technical Report.
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Dissertations and Theses:

• H. Richard Kendall. The Modify-on-Access File System, MS Thesis, Dept of CSE, University of Notre Dame. July 1998.
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Support

• NSF CAREER Award: Collaborative Memory
• HTMT Project
• Schmidt Fellowship
• Notre Dame Faculty Development Award

Disclaimer

The following are included in partial fulfillment of terms of NSF award.

• This material is based upon work supported by the National Science Foundation under Grant No. 9876073.
• Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.