Number of Read/Write Heads

Each hard disk platter has two surfaces, one on each side of the platter. Both surfaces of the platter are used for data on modern drivesSince most hard disks have one to four platters, most hard disks have between two and eight heads.

Only one head can read from or write to the hard disk at a given time. Special circuitry is used to control which head is active at any given time.

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