Varan and Mx: Safe Software Updates via Multi-version Execution

Speaker:        Dr. Cristian Cadar
                Imperial College London

Title:          "Varan and Mx: Safe Software Updates via Multi-version

Date:           Wednesday, 28 January 2015

Time:           4:00pm - 5:00pm

Venue:          Room 3588 (via lifts 27/28), HKUST


Software systems are constantly evolving, with new versions and patches
being released on a continuous basis.  Unfortunately, software updates
present a high risk, with many releases introducing new bugs. We propose
tackling this problem using a simple but effective multi-version execution
approach.  Whenever a new update becomes available, instead of upgrading
the software to the new version, we run the new version in parallel with
the old one, potentially running several different versions concurrently.
By carefully coordinating their execution, we create a more dependable
multi-version application.

In this talk, I present two instances of this idea: Varan, a
high-performance multi-version execution system that allows transparent
failover when one of the versions crashes, and Mx, a multi-version
execution system that can handle certain types of crashes occurring at
different times across versions.  Time remaining, I will present other
applications of multi-version execution, such as record-replay and live


Cristian Cadar leads the Software Reliability Group ( in
the Department of Computing at Imperial College London.  His research
interests span the areas of software engineering, computer systems and
security, with an emphasis on designing practical techniques for improving
the reliability and security of software systems.  Cristian received a PhD
in Computer Science from Stanford University, and undergraduate and
Master's degrees from the Massachusetts Institute of Technology.