Speaker: Angela Demke Brown Title: Online File System Consistency Checking with Low Overhead Abstract: Existing file-system reliability methods, such as checksums, redundancy, or transactional updates, provide limited defenses against file-system bugs that cause disk corruption. The existing workarounds, based on using backups or repairing the file system, are painfully slow. Worse, the recovery is performed long after the error occurred, and thus may result in further corruption and data loss. In this talk, we present a framework that protects file system metadata from buggy file system operations. Our approach leverages modern file systems that provide crash consistency using transactional updates. By checking the consistency of each transaction before it commits, we can minimize the damage caused by file system bugs. The major challenges to this approach are specifying consistency invariants, and correctly interpreting file system behavior without relying on the file system code. We show how to interpret metadata and check consistency invariants for the Linux ext3 file system in our framework. Using this framework, we can detect random as well as targeted file-system corruption at runtime as effectively as the offline e2fsck file-system checker, with low performance overhead. Brief bio: Dr. Angela Demke Brown is an Assistant Professor at the University of Toronto. She received her Ph.D. from Carnegie Mellon University in 2005. Her research interests span the intersection of programming languages and operating systems, with a focus on applying high-level static or dynamic analysis tools to improve the performance and reliability of low-level systems software.