A hard disk drive (HDD) is a fundamental, non-volatile data storage device found in computers and servers, designed for long-term retention of digital information even when powered off. At its core, an HDD stores data magnetically on rapidly rotating, rigid platters coated with a thin magnetic film. These platters, typically made of aluminum or glass, are stacked on a central spindle driven by a high-precision spindle motor spinning at speeds ranging from 5,400 to 15,000 revolutions per minute (RPM). Data is written to and read from these platters using an array of read/write heads, one per platter surface. These heads are mounted on a moving actuator arm assembly, which swiftly positions them over specific tracks (concentric circles) on the platters with nanometer-scale precision.