How hard drives read data

Hard Drive Heads

Ever wondered what actually reads your pictures, movies and documents from your hard drive?

Well… many people falsely believe that data on a computer is actually stored in 1’s and 0’s, as it is often thought. But if your data is stored on a hard drive, which is usually the case (excluding SSD Drives), then your data is not stored in 1’s and 0’s. Your data is actually stored as an analog signal rather than a digital one. To be more specific, your data is stored magnetically on a platter surface or often multiple platter surfaces. One hard drive platter has two surfaces which are made out of either glass or aluminum. These platters are coated with several layers, which among them count a magnetic layer and a very thin lubrication film. Your hard drive creates magnetic fields over which the hard drives’ read / write heads hoover and read the magnetic impulse signal. The read and write heads are very small and exceptionally fragile.

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A picture taken with a microscope at our lab showing the read head element

They are connected to a slider and arm that moves them across the platter surface. The proper term for the arm is called actuator. When a hard drive fails and produces clicking sounds, it indicates in most cases that one of the read / write heads has become damaged. This most frequently occurs due to either wear and tear, manufacturing defect, shock to the drive or excessive heat. This is a common failure that has increased in recent years. In addition to what has already been described as common causes for such failures, a trending factor in recent years has been to lower the head density which has caused a higher percentage of physical failure rate on 1-4TB drives. Hard drives manufacturers keep increasing the total storage capacity, but within the same breath keep the same physical size and diameters of the platters where the data is stored. This is of course to adhere to the trends and demands to keep technology compact. In order to meet such demands it requires the data to be stored with increasingly higher density. Hard drive manufactures have been lowering the flying heights of the heads in respect to the platters. In order to properly read the magnetic impulses on such high density with a low error rate. This however means, that the heads of a hard drive are now even closer to the platter surfaces and even minor contamination or shock can become deadly to your drive and ultimately to your data.

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