Data Access Optimization in Hard Disk Drives

Usage of inertial mechanical units in hard disk drives construction strongly limits the time of access to the information. At the average it takes the hard disk drive about 15 milliseconds to search the track and wait for necessary sector. Hard disk drives manufacturers use various technologies that allow accelerating data exchange - read ahead, lazy write, command overlapping, command queuing optimization. It enables increasing of the hard disk drive performance, reducing quantity of physical calls to the magnetic disk, and allows the hard disk drive to perform readings or writings even at the busy bus. Usage of lazy write technology and of read ahead requires presence of the fast random access memory in the hard disk drive; the size of the random access memory in modern hard disk drives reaches 32 Mb.