Image Migration In A Three Level Data Base Archive System
R. Martinez, Charnchai Archwamety · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1988
Data base archive systems (DBAS) for picture archiving and communications systems (PACS) require very large storage devices for the digital images. The images, as large as 50 Mega-bits, are stored and retrieved simultaneously at the DBAS. The response time to the user for image storage and retrieval must be of the order of two seconds. Consequently, the image storage at the DBAS must be efficient to process the image requests in the required time. This paper describes an image migration algorithm for efficiently storing and moving the images within the DBAS storage devices. The DBAS storage devices are structured in a three level hierarchical architecture. Level 1 is composed of high speed magnetic disks and contains recent images, up to seven days. Level 2 consists of automatic juke box optical disk systems and contains images up to 30 days old. Level 3 is a manual juke box optical disk system and contains storage for images up to 7-10 years. A fourth level is a manual archive for images greater than seven years. The DBAS migration algorithm was developed to migrate images within this three level storage structure. A migration model was developed to represent the image data flow between levels. The model can be used to determine the size of each level at any time and the amount of data flow between levels. The model is driven by image generation requests by the Imaging Equipment and image retrieval requests by the user workstations. The migration algorithm for the DBAS was included in the simulation of the entire PACS system, including the Image Network, DBAS, Imaging Equipment, and User Workstations. This paper presents the result of the simulation and shows the effect of the image migration algorithm on the channel utilization.