TOKYO -- Toshiba Corporation today announced its development of a multimedia server architecture that can provide highly efficient and cost-effective video- and information-on-demand services to hundreds of users simultaneously. The new server architecture, SmartStreamer, is expected to reduce the system cost to one-fifth that of other experimental or commercial systems, and paves the way to practical on-demand services operated by CATV companies and other service providers.

Commercial on-demand services require distribution of massive volumes of diverse data to large numbers of consumers at the same time. The main approach to achieving this has been use of massively parallel processors computers or advanced workstations as servers in large-scale systems for more than 1000 subscribers. However, the high system cost is an obstacle for affordable on-demand services. Toshiba's SmartStreamer is the ideal candidate for lower-cost large-scale on-demand systems.

The key to SmartStreamer is its newly developed stream switch array based on the IC-memories and ASICs. The array provides a dedicated data transfer route that facilitates flows of data from hard disks to the network. The new architecture achieves a server system offering a data transfer rate ten times faster than other systems. Not only does the array support continuous distribution of multiple data, it reduces the number of hard disks and the number of computers required for the system.

1. System outline

SmartStreamer consists of a scheduling processor, five disk controllers (for data retrieval from hard disk drives), four network control devices that output data, and the IC-memory and ASIC-based memory switch array. Requests from subscribers are fed to the scheduling processor and it commands disk controllers to deliver the required data. These data are downloaded to the memory switch array, where it is temporarily stored before switching to the network controller for output to the user. With four network controllers each supporting 60 data streams, the memory switch array can support distribution to approximately 240 network outputs at a time. Larger numbers of subscribers will be supported by clusters of servers.

2. Simultaneous and continuous data distribution

The disc controllers retrieve desired data at high speed, at the command of the dedicated scheduling processor. Data are transferred in packets to an area in the memory switch array reserved for the subscriber making the request, and then sent to the network control device. Before the network control device finishes sending out this data, the next data sequence is already being retrieved and transferred to another reserved memory area, ready for the next distribution phase.

3. Reliable Architecture

The new system assures highly reliable performance by storing parity data along with the other data on hard disk drive array. If data on a hard disk becomes corrupted, the logic circuits in the stream switch array support data restoration by processing data retrieved from another hard disk and offers continuous operation without any interruption in service.

4. New algorithm

A new algorithm for controlling orders of data storage in the memory switch array realizes quick responses to subscribers demands. In 90% of cases, the system responds within one second of receiving a demand from a subscriber, a rate more than three times faster than that of other systems based on different technologies.