There are two technology trends strongly impacting the design and performance of I/O systems. First, processor power, especially for single (or few) chip designs, is increasing very rapidly, leading to: (a) (almost) corresponding increases in I/O load, (b) distributed systems with workstations (w/wo local disks), file servers and computation nodes, and (c) multiprocessors with enormous cost/performance advantages over uniprocessors providing the same aggregate performance. Second, disk storage densities are increasing rapidly without any comparable increase in disk performance. A number of design and optimization problems have become extremely important due to these trends: (a) Systems are becoming increasingly susceptible to I/O bottlenecks due to increasing I/O rates and the less quickly in creasing ability of the I/O system to respond to them. (b) Multiprocessor systems with shared I/O devices and/or databases are increasingly susceptible to I/O bottlenecks in referencing, locking and updating shared data. This project continues research on a number of topics relating to file, I/O and database system performance. These include: (a) Development and analysis of algorithms for disk caching in distributed and hierarchical systems, taking into account both consistency and performance. (b) Studies of the effect of disk caching in conjunction with disk striping and log structured file systems. (c) Analysis and development of locking algorithms for shared, distributed database systems. (d) Design, optimization and implementation of hierarchical and distributed file migration in a very large mass storage systems using optical disks to be built at UC Berkeley. The work relies heavily on actual system measurement and trace driven simulation.
