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Lakshmi N. Bairavasundaram<br>
<span style="font-size: 12; color: black; font-weight: normal">Email: <b>laksh</b> AT SERVER <b>cs.wisc.edu</b></span>
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My full name is Lakshmi Narayanan Bairavasundaram.
I'm a Ph.D. student in <a href="http://www.cs.wisc.edu" target="_blank">Computer
Sciences</a> at <a href="http://www.wisc.edu" target="_blank">University
of Wisconsin-Madison</a>. My research area is Operating systems.
I work in the <a href="http://www.cs.wisc.edu/adsl" target="_blank">ADvanced Systems
Laboratory</a>, and my advisors are <a href="http://www.cs.wisc.edu/%7Edusseau"
target="_blank">Prof. Andrea C. Arpaci-Dusseau</a> and <a
href="http://www.cs.wisc.edu/%7Eremzi" target="_blank">Prof. Remzi H. Arpaci-Dusseau</a>.
<br>
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<br>
<h3>
Resume:
[<a href="./resume/resume.pdf" target="_blank">PDF</a>]
<span style="font-size: 11; color: black; font-weight: normal">(Last updated: Jan 2, 2008)</span>
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<h2><b><u><a name="Research"></a>Research</u></b></h2>
<p></p>
<br>
My research interests include File and Storage Systems, Operating Systems, and Fault Tolerance.
<br>
<br>
<b>Dissertation</b>:
My dissertation focuses on the characteristics, impact and tolerance of <i><b>partial disk failures</b></i>. Disk drives fail in complex ways.
In most of these cases, the disk does not stop working entirely; the failures tend to be partial failures, where some disk
sectors are unavailable due to a latent sector error or some disk blocks are silently corrupted. The goals of my dissertation
are to understand the characteristics of partial failures, analyze how these failures impact various components of the
storage stack, and develop solutions to tolerate such failures.
As part of my dissertation, I have analyzed the occurrence and characteristics of latent sector errors in disk drives
[<a href="http://www.cs.wisc.edu/adsl/Publications/latent-sigmetrics07.html" target=_blank>SIGMETRICS07</a>].
The study found that a significant percentage (20%) of nearline disks may be affected in 2 years
of use, and that latent sector errors show high spatial and temporal locality. Given that partial failures could affect a
significant percentage of disks, it is important to understand their impact on different elements of the storage stack.
I (along with other members of my research group) have analyzed the impact of such errors on modern commodity
file systems (IBM JFS, ext3, ReiserFS and Windows NTFS)
[<a href="http://www.cs.wisc.edu/adsl/Publications/iron-sosp05.html" target=_blank>SOSP05</a>,
<a href="http://www.cs.wisc.edu/adsl/Publications/trust-storagess06.html" target=_blank>StorageSS06</a>].
We found that even widely-used
file systems have bugs in failure handling code, use illogically inconsistent policies and do not implement fault
tolerance techniques like type-checking and replication effectively. In addition to file systems, I have also investigated
the policies and mechanisms used by current virtual memory systems (Linux, FreeBSD,Windows XP) to tolerate disk
errors [<a href="http://www.cs.wisc.edu/adsl/Publications/vmdep-dsn06.html" target=_blank>DSN06</a>]
and found that virtual memory systems are equally inconsistent and ineffective at handling partial disk
failures. Given that even widely-used systems have bugs and cannot be trusted to handle disk failures, it is important
to lower the trust we place in any single system. I am currently developing a file system architecture that eliminates
the need to trust a single file system.
<br>
<br>
<b>Other Research</b>: My initial research experience was built
on studying how different layers of a system interact and how "gray-box"
techniques can be used in such layers to overcome the limitations of
narrow interfaces. A specific application of such techniques has been in
<i><b>semantically-smart disk systems</b></i>. These are disk systems that leverage
basic knowledge of file system operation to provide significant
improvements in performance, availability and security. I have primarily
explored the performance angle. I have developed a cache mechanism for
disk arrays that utilizes basic knowledge of file system data structures
to provide an exclusive cache i.e. a cache that retains blocks that are
not present in the file system cache [<a href="http://www.cs.wisc.edu/adsl/Publications/xray-isca04.html" target=_blank>ISCA04</a>].
I have also extended this technique to work effectively with database systems
[<a href="http://www.cs.wisc.edu/adsl/Publications/sdsdb-fast05.html" target=_blank>FAST05</a>]. Finally, I
have worked on using block liveness information in a semantically-smart
disk [<a href="http://www.cs.wisc.edu/adsl/Publications/life-osdi04.html" target=_blank>OSDI04</a>].
In addition to my research at Madison, I have been on research internships at
IBM T. J. Watson Research Center, NY (June-Aug 2004), where I developed a distributed caching
mechanism for storage systems, Intel Corporation, OR (May-Aug 2005), where I developed
techniques for hypervisor-based fault injection, and Network Appliance, CA
(Jun-Aug 2006, Jun-Aug 2007) where I analyzed data on storage system errors.
<br>
<br>
<br>
<hr noshade>
<h2><b><u><a name="Publications"></a>Publications</u></b></h2>
<p></p>
<span style="font-weight: bold;"><br>
An Analysis of Data Corruption in the Storage Stack</span><br>
Lakshmi N. Bairavasundaram, Garth R. Goodson, Bianca Schroeder, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau <br>
<span style="font-style: italic;">
To appear in the Proceedings of the 6th USENIX conference on File and Storage Technologies (FAST'08)<br>
San Jose, California. February 2008.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/corruption-fast08.html" target=_top>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/corruption-fast08.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/corruption-fast08.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/corruption-fast08.bib" target=_top>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
Parity Lost and Parity Regained</span><br>
Andrew Krioukov, Lakshmi N. Bairavasundaram, Garth R. Goodson, Kiran Srinivasan, Randy Thelen, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau <br>
<span style="font-style: italic;">
To appear in the Proceedings of the 6th USENIX conference on File and Storage Technologies (FAST'08)<br>
San Jose, California. February 2008.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/parity-fast08.html" target=_top>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/parity-fast08.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/parity-fast08.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/parity-fast08.bib" target=_top>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
An Analysis of Latent Sector Errors in Disk Drives</span><br>
Lakshmi N. Bairavasundaram, Garth R. Goodson, Shankar Pasupathy, Jiri Schindler. <br>
<span style="font-style: italic;">
Proceedings of the International Conference on Measurement and Modeling of Computer Systems (SIGMETRICS'07). <br>
San Diego, California. June 2007.</span><br>
<span style="font-weight: bold; color: red;">Kenneth C. Sevcik Outstanding Student Paper Award!</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/latent-sigmetrics07.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/latent-sigmetrics07.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/latent-sigmetrics07.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/latent-sigmetrics07.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
Limiting Trust in the Storage Stack</span><br>
Lakshmi N. Bairavasundaram, Meenali Rungta, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau <br>
<span style="font-style: italic;">
Proceedings of the 2nd International Workshop on Storage Security and Survivability (StorageSS'06) <br>
Alexandria, Virgina. October 2006.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/trust-storagess06.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/trust-storagess06.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/trust-storagess06.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/trust-storagess06.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
Dependability Analysis of Virtual Memory Systems</span><br>
Lakshmi N. Bairavasundaram, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau <br>
<span style="font-style: italic;"> Proceedings of International Conference on Dependable Systems and Networks (DSN'06) <br>
Philadelphia, Pennsylvania. June 2006.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/vmdep-dsn06.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/vmdep-dsn06.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/vmdep-dsn06.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/vmdep-dsn06.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
Semantically-Smart Disk Systems: Past, Present, and Future</span><br>
Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau, Lakshmi N. Bairavasundaram, Timothy E. Denehy, Florentina I. Popovici, Vijayan Prabhakaran, Muthian Sivathanu<br>
<span style="font-style: italic;"> Sigmetrics Performance Evaluation Review (PER) <br>
Volume 33, Number 4. March 2006.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/sds-per06.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/sds-per06.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/sds-per06.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/sds-per06.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
Database Aware Semantically-smart Storage</span><br>
Muthian Sivathanu, Lakshmi N. Bairavasundaram, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau<br>
<span style="font-style: italic;"> Proceedings of the 4th USENIX conference on File and Storage Technologies (FAST'05)<br>
San Francisco, California. December 2005.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/sdsdb-fast05.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/sdsdb-fast05.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/sdsdb-fast05.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/sdsdb-fast05.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
IRON File Systems</span><br>
Vijayan Prabhakaran, Lakshmi N. Bairavasundaram, Nitin Agrawal, Haryadi S. Gunawi, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau <br>
<span style="font-style: italic;"> Proceedings of 20th ACM Symposium on Operating Systems Principles (SOSP'05) <br>
Brighton, United Kingdom. October 2005.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/iron-sosp05.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/iron-sosp05.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/iron-sosp05.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/iron-sosp05.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
Life or Death at Block Level</span><br>
Muthian Sivathanu, Lakshmi N. Bairavasundaram, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau <br>
<span style="font-style: italic;"> Proceedings of 6th Symposium on Operating Systems Design and Implementation (OSDI'04)<br>
San Francisco, California. December 2004.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/life-osdi04.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/life-osdi04.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/life-osdi04.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/life-osdi04.bib" target=_blank>BibTex</a>
<br>
<span style="font-weight: bold;"><br>
X-RAY: A Non-Invasive Exclusive Caching Mechanism for RAIDs</span><br>
Lakshmi N. Bairavasundaram, Muthian Sivathanu, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau<br>
<span style="font-style: italic;">Proceedings of the 31st Annual International Symposium on Computer Architecture (ISCA'04)<br>
Munich, Germany. June 2004.</span><br>
Available as:
<a href="http://www.cs.wisc.edu/adsl/Publications/xray-isca04.html" target=_blank>Abstract</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/xray-isca04.pdf" target=_blank>PDF</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/xray-isca04.ps" target=_blank>Postscript</a>
<a href="http://www.cs.wisc.edu/adsl/Publications/xray-isca04.bib" target=_blank>BibTex</a>
<br>
<br>
<b>Dynamic Path Profile Aided Recompilation in a JAVA Just-In-Time Compiler</b><br>
R. Vinodh Kumar, B. Lakshmi Narayanan, R. Govindarajan <br>
<i>Proceedings of the International Conference on High Performance Computing (HiPC'02)<br>
Bangalore, India. December 2002.</i><br>
Available as: <a href="research/dynpath.pdf">PDF</a>
<br>
<b><br>
Functional Unit Usage Based Thread Selection in a Simultaneous Multithreaded Processor</b> <br>
Deepak Babu M.I, Lakshmi Narayanan B, Madhu Saravana Sibi G, Ranjani Parthasarathi <br>
<i>Poster Session of the International Conference on High Performance Computing (HiPC'01)<br>
Hyderabad, India. December 2001.</i>
<br>
Available as: <a href="research/hipc.pdf">PDF</a>
<br>
<br>
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<h2><b><u><a name="Internships"></a>Internships</u></b></h2>
<p></p>
<br>
<b>Summer Intern. Advanced Development Group, Network Appliance.</b><br>
<i>Sunnyvale, CA. June - August, 2007. </i><br>
I analyzed the occurrence of silent data corruption in disk drives, identifying important
characteristics that would be useful for corruption-proof system design.
<br><br>
<b>Summer Intern. Advanced Development Group, Network Appliance.</b><br>
<i>Sunnyvale, CA. June - August, 2006. </i><br>
I analyzed data on latent sector errors (disk errors wherein a sector becomes inaccessible),
examining the dependence on factors such as disk drive age and capacity, and identifying
characteristics such as spatial and temporal locality.
<br><br>
<b>Summer Intern. Core Virtualization Research Group, Intel Corporation.</b><br>
<i>Hillsboro, OR. May - August, 2005.</i> <br>
I developed techniques for hypervisor-based fault injection and applied these techniques to study
operating system behavior when memory and disk errors occur.
<br><br>
<b>Summer Intern. IBM T.J. Watson Research Center.</b><br>
<i>Hawthorne, NY. May - August, 2004.</i> <br>
I designed and implemented an extensible and scalable distributed cache architecture for an
enterprise storage system. My scheme involved the use of remote memory (on machines over a
high-speed LAN) for caching disk blocks.
<br><br>
<b>Summer Research Fellow. Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR)</b><br>
<i>Bangalore, India. May - June, 2001. </i><br>
I developed an instruction scheduler for a Java Just-in-Time compiler.
The scheduler was built to utilize path profile information.
<br><br>
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