Hard Disk Drives Basics
Imagine a layer of CDs referred to as 'platters'. They are read by arms. A platter contains thousands of tracks, which are collections of sectors. A sector is a basic read-write unit, typically 512-4096 bytes big. A sector typically looks like [ID | Data | ECC], so some data to identify it, the actual data, and some error-correcting code that can be used in case of minor physical failures.