Storage

In 1987, three researchers at the University of California, Berkeley published a paper that would fundamentally change how we think about data storage. David Patterson, Garth Gibson, and Randy Katz proposed something counterintuitive: instead of buying one expensive, reliable disk drive, why not combine many cheap, unreliable ones into a system more reliable than any single drive could ever be? They called it RAID—Redundant Arrays of Inexpensive Disks. The insight was mathematical, not magical. By distributing data across multiple drives with carefully calculated redundancy, you could achieve both performance and reliability that would be impossible with a single disk. The key was a simple operation that most programmers learn in their first computer science course: XOR. ...

When you save a file to a solid-state drive, something happens at the atomic level that your hard drive could never accomplish. Electrons tunnel through an insulating barrier and become trapped in a microscopic cage, where they can remain for years without power. This is the fundamental magic of flash memory—and understanding it explains everything from why SSDs slow down when full to why they eventually wear out. The first commercial flash memory chip appeared in 1988, but the technology traces back to a 1967 paper by Dawon Kahng and Simon Sze at Bell Labs. They proposed storing charge in a transistor’s floating gate—a conductive layer completely surrounded by insulator. Nearly six decades later, every NAND flash cell operates on this same principle, even as manufacturers have stacked cells hundreds of layers high and squeezed multiple bits into each one. ...