Introduction

The magnetic disk drive is the core technology underlying digital asset management. An array of the disks gives users fast and random access to the content repository. The ever increasing capacity and read/write speeds of the drives has enabled document storage, then images, and finally video. The capacity has increased to 40,000 times the original in 50 years since the drive was developed. These advances promise to increase apace until the limits imposed by the laws of physics. We will then have to turn to other technologies.

Disk performance is increasing year on year, while the cost falls. This means that ever-larger media libraries can be online to give almost instantaneous access to the content. One only has to look at the video post-production industry to see how the disk has taken over from tape as the medium for editing. Videotape is only used for capture and archiving.

The disk architecture is an important factor in the overall system design. If you were to choose a less than optimum architecture, there will be long latencies for file recall, and also the number of simultaneous clients that can use the system will be limited. These factors are even more important if your archives include video content. This is because of the very large files sizes and the bandwidth required for real-time record and playback.

In a simple asset management system, the content will be stored on a standard computer file server. These are sold for general office use, and may...