caa a22 4500 477132790 CHVBK 20180405111708.0 cr unu---uuuuu 170330e19971101xx s 000 0 eng 10.1007/s005300050070 doi (NATIONALLICENCE)springer-10.1007/s005300050070 Pang HweeHwa Institute of Systems Science, National University of Singapore, Heng Mui Keng Terrace, Kent Ridge, Singapore 119597, Republic of Singapore e-mail: hhpang@iss.nus.sg, SG aut Tertiary storage in multimedia systems: staging or direct access? [Elektronische Daten] [HweeHwa Pang] Abstract.: Multimedia applications that are required to manipulate large collections of objects are becoming increasingly common. Moreover, the size of multimedia objects, which are already huge, are getting even bigger as the resolution of output devices improve. As a result, many multimedia storage systems are not likely to be able to keep all of their objects disk-resident. Instead, a majority of the less popular objects have to be off-loaded to tertiary storage to keep costs down. The speed at which objects can be accessed from tertiary storage is thus an important consideration. In this paper, we propose an adaptive data retrieval algorithm that employs a combination of staging and direct access in servicing tertiary storage retrieval requests. At retrieval time, an object that resides in tertiary storage can either be staged to and then played back from disks, or the object can be accessed directly from the tertiary drives. We show that a simplistic policy that adheres strictly to staging or direct access does not exploit the full retrieval capacity of both the tertiary library and the secondary storage. To overcome the problem, we propose a data retrieval algorithm that dynamically chooses between staging and direct access, based on the relative load on the tertiary versus secondary devices. A series of simulation experiments confirms that the algorithm achieves good access times over a wide range of workloads and resource configurations. Moreover, the algorithm is very responsive to changing load conditions. Springer-Verlag Berlin Heidelberg, 1997 Key words:Multimedia server - Storage hierarchy - Tertiary library - Data migration - Feedback control nationallicence https://doi.org/10.1007/s005300050070 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s005300050070 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Pang HweeHwa Institute of Systems Science, National University of Singapore, Heng Mui Keng Terrace, Kent Ridge, Singapore 119597, Republic of Singapore e-mail: hhpang@iss.nus.sg, SG aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer