DATE: Thursday, May 1, 2003
TIME: Noon - 1 pm
PLACE: Wean Hall 8220

Remzi H. Arpaci-Dusseau
University of Wisconsin

Semantically-Smart Disk Systems

There is a knowledge gap in the world of storage. File systems have plenty of high-level knowledge; for example, they know how files are laid out on disk, which files are in which directories, and the current state of which blocks are free and which are utilized. Storage systems (i.e., RAIDs), in contrast, have plenty of low-level knowledge; for example, they know about scheduling algorithms, exact head positions, and the RAID scheme that is employed. Unfortunately, many interesting classes of functionality demand both high-level and low-level knowledge. In current systems, such knowledge is difficult or impossible to obtain.

In this talk, I will present a new approach to unifying and exploiting these disparate pieces of knowledge within what we call a "semantically-smart" disk system (SDS). As opposed to a typical "smart" disk system, an SDS has detailed knowledge of how the file system above is using the storage system, including information about the file system on-disk data structures and policies. An SDS exploits this knowledge to transparently improve performance or enhance functionality beneath a standard block interface (e.g., SCSI).

I will discuss some of the important hurdles one must overcome in building an SDS, including how an SDS can automatically obtain file-system specific information, and the overheads involved in doing so. I will then present a number of case studies that demonstrate functionality or performance improvements that would be difficult or impossible to implement within a more traditional framework. In our initial work, we have found that a surprising amount of functionality can be embedded within an SDS, hinting at a future where disk manufacturers can compete on enhanced functionality and not simply cost-per-byte and performance.

Remzi Arpaci-Dusseau is an assistant professor in the Department of Computer Sciences at the University of Wisconsin, Madison. He received his B.S. in Computer Engineering from the University of Michigan, Ann Arbor, and M.S. and Ph.D. in Computer Science from the University of California, Berkeley. His research interests include storage systems, operating systems, parallel and distributed systems, high-performance applications, databases, and computer architecture. Remzi is primarily interested in developing and understanding the key technologies that will be crucial in building the next generation of manageable, robust, and high-performance storage systems.


For Further Seminar Info:
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