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Acceleration methods of accessing data in the HDD

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 drive about 15 milliseconds to search the track and wait for the necessary sector. Storage devices manufacturers use various technologies that allow accelerating data exchange - read ahead, lazy write, command overlapping, command queuing optimization. It enables increasing of the HDD performance, reducing the quantity of physical calls to the magnetic disk, and allows the hard drive to perform readings or writings even at the busy bus. Usage of lazy write technology and of read ahead requires the presence of the fast random access memory in the HDD. The size of the random access memory in modern hard disk drives reaches 64 MB.