Check out the new USENIX Web site.

Home About USENIX Events Membership Publications Students
FAST '03 Abstract

Metadata Efficiency in Versioning File Systems

Craig A. N. Soules, Garth R. Goodson, John D. Strunk, and Gregory R. Ganger, Carnegie Mellon University

Abstract

Versioning file systems retain earlier versions of modified files, allowing recovery from user mistakes or system corruption. Unfortunately, conventional versioning systems do not efficiently record large numbers of versions. In particular, versioned metadata can consume as much space as versioned data. This paper examines two space-efficient metadata structures for versioning file systems and describes their integration into the Comprehensive Versioning File System (CVFS), which keeps all versions of all files. Journal-based metadata encodes each metadata version into a single journal entry; CVFS uses this structure for inodes and indirect blocks, reducing the associated space requirements by 80%. Multiversion b-trees extend each entry’s key with a timestamp and keep current and historical entries in a single tree; CVFS uses this structure for directories, reducing the associated space requirements by 99%. Similar space reductions are predicted via trace analysis for other versioning strategies (e.g., on-close versioning). Experiments with CVFS verify that its current-version performance is sim-ilar to that of non-versioning file systems while reducing overall space needed for history data by a factor of two. Although access to historical versions is slower than con-ventional versioning systems, checkpointing is shown to mitigate and bound this effect.
  • View the full text of this paper in HTML and PDF.
    Click here if you have forgotten your password Until May 2004, you will need your USENIX membership identification in order to access the full papers. The Proceedings are published as a collective work, © 2003 by the USENIX Association. All Rights Reserved. Rights to individual papers remain with the author or the author's employer. Permission is granted for the noncommercial reproduction of the complete work for educational or research purposes. USENIX acknowledges all trademarks within this paper.

  • If you need the latest Adobe Acrobat Reader, you can download it from Adobe's site.
To become a USENIX Member, please see our Membership Information.

?Need help? Use our Contacts page.

Last changed: 7 Nov. 2003 jel
Technical Program
FAST '03 Home
USENIX home