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