PERFORMANCE OF A STORAGE-SYSTEM FOR SUPPORTING DIFFERENT VIDEO TYPES AND QUALITIES

Future video-on-demand (VoD) servers will need to support many existin g and emerging video data types, These data types include 15-fps (fram es per second) animation, 30-fps National Television Systems Committee (NTSC) quality video, and 60-fps high definition television (HDTV vid eo. The different display speeds and frame sizes of these various vide o types impose a major constraint on the design of VoD storage systems , This paper presents the results of an experimental study, conducted on a Silicon Graphics Inc, (SGI) Onyx computer system, that investigat ed the impact of these video types on the design of a VoD storage syst em, The key issues involved in supporting these different video types in a VoD environment are as follows: 1) the video allocation method an d 2) the proper block size (a ''block'' is a basic unit of several con tiguous,ideo frames that Hill be accessed from several disks each time a request is made) to use for data striping and retrieval, Two alloca tion schemes, logical volume striping and application level striping, along with varying frame and block sizes for each of the three differe nt video data types are examined in this paper, The focus of our study is to determine the maximum number of concurrent accesses that can be supported with a guaranteed quality-of-service (QoS), The degree of s calability (i.e., striping data over more disk arrays) of the experime ntal VoD system used is also studied, Based on our experimental result s, application level striping demands smaller block sizes for all thre e video types, and more concurrent accesses can be distributed over th e storage devices, The experimental results demonstrate that applicati on level striping has excellent scalability for animation and NTSC vid eos.