Latency reduction for CD-ROM and CLV disks

In a conventional magnetic storage subsystem, rotational latency is a major component of the basic service time for an I/O access. In CD-ROMs, where the rotational speed is one order of magnitude slower than that of magnetic disks, latency's role is even greater. While simple latency techniques using data replication have already been proposed for conventional magnetic disks, such techniques can not be directly applied to CD-ROMs, because, unlike conventional magnetic disks which are consist angular velocity (CAV) devices, CD-ROMs employ the constant linear velocity (CLV) scheme. Instead of many concentric tracks, there is only one long continuous spiral per surface. In this paper, a data replication technique for reducing average latency is proposed for CD-ROMs and other CLV disks. This technique is analyzed in terms of the reduction in average latency and the impact on storage capacity.<>