RAID architectures have been used for more than two decades to recover data upon disk failures. Disk failure is just one of the many causes of damaged data. Data can be damaged by virus attacks, user errors, defective software/firmware, hardware faults, and site failures. The risk of these types of data damage is far greater than disk failure with today’s mature disk technology and networked information services.  It has therefore become increasingly important for today’s disk array to be able to recover data to any point in time when such a failure occurs. This talk presents a new disk array architecture that provides Timely Recovery to Any Point-in-time, referred to as TRAP-Array. TRAP-Array stores not only the data stripe upon a write to the array, but also the time-stamped Exclusive-ORs of successive writes to each data block. By leveraging the Exclusive-OR operations that are performed upon each block write in today’s RAID4/5 controllers, TRAP does not incur noticeable performance overhead. More importantly, TRAP is able to recover data very quickly to any point-in-time upon data damage by tracing back the sequence and history of Exclusive-ORs resulting from writes. What is interesting is that TRAP architecture is amazingly space-efficient. We have implemented a prototype TRAP architecture using software at block device level and carried out extensive performance measurements using TPC-C benchmark running on Oracle and Postgress databases, TPC-W running on MySQL database, and file system benchmarks running on Linux and Windows systems. Our experiments demonstrated that TRAP is not only able to recover data to any point-in-time very quickly upon a failure but it also uses less storage space than traditional daily differential backup/snapshot. Compared to the state-of-the-art continuous data protection technologies, TRAP saves disk storage space by one to two orders of magnitude with a simple and a fast encoding algorithm. From an architecture point of view, TRAP-Array opens up another dimension for storage arrays. It is orthogonal and complementary to RAID in the sense that RAID protects data in the dimension along an array of physical disks while TRAP protects data in the dimension along the time sequence.

Professor Yang's research has been sponsored mainly by the National Science Foundation (NSF). He has authored and coauthored numerous technical articles in such journal as IEEE Transactions on Computers, IEEE Transaction on Parallel and Distributed Systems, IEEE Computer and Journal for Parallel and Distributed Computing, along with paper presented at International Symposium on Computer Architectures, International Symposium on High Performance Computer Architectures, International Conference on Parallel Processing, and International Conference on Internet Computing, etc. He holds several U.S. patents and has also contributed a number of chapters to books in the field of computer engineering. Graduate students who have graduated under his advice usually work in computer industry or research institutions as computer engineers, design architects, or research scientists. Dr. Yang has served as program chair, committee members for several professional conferences in the field and guest edited special issues for professional journals. He is an associate editor of IEEE Transaction on Parallel and Distributed Systems. He is an IEEE-Computer Society distinguished speaker of the year, (1996-99). A senior member of IEEE Computer Society and a member of ACM, his research interests are in: Computer Architectures, Parallel and Distributed Computing (software and hardware), Computer Performance Modeling and Simulation, Data Storage and I/O architectures, Computer Applications and Storage Networking (SAN, NAS, and LAN).