Data Layouts for Digital Video Servers 1 Ariel

We present a novel data organization for disk arrays|Segmented Information Dispersal (SID). SID provides protection against disk failures while ensuring that the reconstruction of the missing data requires only relatively small contiguous accesses to the available disks. SID has a number of properties that make it an attractive solution for fault-tolerant video servers. Under fault-free conditions, SID performs as well as RAID 5 and organizations based on balanced incomplete block designs (BIBD). Under failure, SID performs much better than RAID 5 since it signiicantly reduces the size of the disk accesses performed by the reconstruction process. SID also performs much better than BIBD by ensuring the contiguity of the reconstruction accesses. Contiguity is a very signiicant factor for video retrieval workloads, as we demonstrate in this paper. We present SID data organizations with a concise representation which enables the reconstruction process to locate eeciently the needed video and check data.