Contact

Vijayan Prabhakaran
email
me.jpg

About me

I graduated with a Ph.D. from the Computer Sciences Department at the University of Wisconsin, Madison in June 2006. I studied under the guidance of Prof. Andrea C. Arpaci-Dusseau and Prof. Remzi H. Arpaci-Dusseau.

Currently, I work with a fantastic set of people at Datrium. Before that, I spent 6 wonderful years at Microsoft Research, Silicon Valley.

My interests are in the broad area of Operating Systems. Specifically, I'm interested in file and storage systems. My dissertation was on IRON File Systems.

Research

My doctoral research focused on understanding how commodity file systems handle various types of modern disk failures and examined ways to build file systems with Internal RObustNess (IRON) against disk errors.
 
Disk drives are widely used as a primary medium for storing information. While commodity file systems trust disks to either work or fail completely, modern disks exhibit complex failure modes such as latent sector faults and block corruptions, where only portions of a disk fail. In this thesis, we focus on understanding the failure policies of file systems and improving their robustness to disk failures. We suggest a new fail-partial failure model for disks, which incorporates realistic localized faults such as latent sector faults and block corruption. We then develop and apply a novel semantic failure analysis technique, which uses file system block type knowledge and transactional semantics, to inject interesting faults and investigate how commodity file systems react to a range of more realistic disk failures.

We apply our technique to five important journaling file systems: Linux ext3, ReiserFS, JFS, XFS, and Windows NTFS. We classify their failure policies in a new taxonomy that measures their Internal RObustNess (IRON), which includes both failure detection and recovery techniques. Our analysis results show that commodity file systems store little or no redundant information, and contain failure policies that are often inconsistent, sometimes buggy, and generally inadequate in their ability to recover from partial disk failures.

We remedy the reliability short comings in commodity file systems by addressing two issues. First, we design new low-level redundancy techniques that a file system can use to handle disk faults. We begin by qualitatively and quantitatively evaluating various redundancy information such as checksum, parity, and replica, Then, in order to account for spatially correlated faults, we propose a new probabilistic model that can be used to construct redundancy sets Finally, we describe two update strategies: a overwrite and no-overwrite approach that a file system can use to update its data and parity blocks atomically without NVRAM support. Overall, we show that low-level redundant information can greatly enhance file system robustness while incurring modest time and space overheads.

Second, to remedy the problem of failure handling diffusion, we develop a modified ext3 that unifies all failure handling in a centralized module. We then showcase the power of centralized failure handling in ext3c, a modified IRON version of ext3 that uses centralized module by demonstrating its support for flexible, consistent, and fine-grained policies. By carefully separating policy from mechanism, ext3c demonstrates how a file system can provide a thorough, comprehensive, and easily understandable failure-handling policy.


Publications

Conference Publications

IRON File Systems, Vijayan Prabhakaran, Lakshmi N. Bairavasundaram, Nitin Agrawal, Haryadi S. Gunawi, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau. Symposium on Operating Systems Principles (SOSP '05) Brighton, United Kingdom, October, 2005.
Available as: Abstract, Postscript, PDF, BibTex

Model-Based Failure Analysis of Journaling File Systems, Vijayan Prabhakaran, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau. International Conference on Dependable Systems and Networks (DSN-2005), Yokohama, Japan, June, 2005.
Available as: Abstract Postscript PDF BibTeX

Analysis and Evolution of Journaling File Systems, Vijayan Prabhakaran, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau. USENIX Annual Technical Conference (USENIX-2005), Anaheim, CA, April, 2005.
Available as: Abstract Postscript PDF BibTeX

Improving Storage System Availability with D-GRAID, Muthian Sivathanu, Vijayan Prabhakaran, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau. Proceedings of the Third USENIX Conference on File and Storage Technologies (FAST-2004), Best Student Paper Award. March 2004 San Francisco, CA, March, 2004
Available as: Abstract Postscript PDF BibTeX

Semantically-Smart Disk Systems, Muthian Sivathanu, Vijayan Prabhakaran, Florentina Popovici, Timothy Denehy, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau. The Second USENIX Conference on File and Storage Technologies (FAST-2003), San Francisco, CA, March, 2003
Available as: Abstract Postscript PDF BibTeX

Journal Publications

Improving Storage System Availability with D-GRAID, Muthian Sivathanu , Vijayan Prabhakaran , Andrea C. Arpaci-Dusseau , Remzi H. Arpaci-Dusseau  ACM Transactions on Storage (TOS) pages 133--170 May 2005 volume 1 number 2
Available as: Abstract PDF BibTeX

Technical Reports

Analysis and Evolution of a Journaling File System, Vijayan Prabhakaran, Andrea C. Arpaci-Dusseau, and Remzi H. Arpaci-Dusseau, UW Technical Report 1509, June 2004.
 
High Throughput Data Transfers using the Tornado Transport Protocol, Vijayan Prabhakaran, Joseph Stanley, Paul Barford, UW Technical Report, October, 2002.

File System Fingerprinting for Semantically-Smart Disk Systems, Vijayan Prabhakaran, Masters' Thesis, University of Wisconsin, May 2003.

Talks

IRON File Systems at the Symposium of Operating Systems Principles, Brighton, U.K., (SOSP2005).

Indexing LUNs: Speeding Up Search at Network Appliance, Aug 2005 (summer intern talk).

Model-Based Failure Analysis of Journaling File Systems at the International Conference on Dependable Systems and Networks (DSN-2005), Yokohama, Japan, June, 2005.

Analysis and Evolution of Journaling File Systems at the USENIX Annual Technical Conference (USENIX-2005), Anaheim, CA, April, 2005.