Solid-state drive

The solid-state drive existed for over a decade before it mattered. In 1991, SanDisk produced a 20 MB SSD for IBM's ThinkPad line—a flash-based storage device with no moving parts, instant access times, and silent operation. It cost $1,000. The hard disk drive it aimed to replace stored more, cost less, and had thirty years of manufacturing optimization behind it. Path dependence would keep the HDD dominant for another two decades.

The SSD emerged from converging lineages at exactly the moment those lineages first intersected. Fujio Masuoka invented flash memory at Toshiba in 1980, building on EEPROM technology. Toshiba released NAND flash in 1987—higher density and lower cost than the earlier NOR flash variant. Eli Harari, who had pioneered thin-oxide processing at Hughes Aircraft in the 1970s, co-founded SunDisk (later SanDisk) in 1988 specifically to commercialize flash for storage applications. The 1991 prototype coupled a flash array with an intelligent controller that could interface with standard IBM laptop hardware. The technology worked. The economics did not.

In 1991, a 20 MB SSD cost $50,000 per gigabyte. Even NAND flash, cheaper than earlier variants, remained several times more expensive than DRAM. The HDD, despite its mechanical fragility—spinning platters, moving read heads, susceptibility to shock—had a three-decade head start in manufacturing scale and learning curve optimization. Every factory, every supply chain, every software assumption was built around the HDD's characteristics. The SSD was not competing against physics; it was competing against accumulated path dependence.

The crossover point came in 2004 when NAND flash prices dropped below DRAM prices for the first time. This changed everything. By 2020, the cost per gigabyte had plummeted from $50,000 to less than $0.05—a million-fold reduction in thirty years. Moore's Law applied to solid-state storage with a vengeance that spinning platters could not match.

The SSD did not merely replace the HDD; it enabled applications the HDD could never support. Instant boot times transformed laptop usability. Shock resistance made mobile devices practical. Low power consumption extended battery life. Most critically, the random access speeds—thousands of times faster than seek times on spinning platters—made modern cloud computing architectures possible. The data centers powering AI training runs could not function with mechanical storage. The SSD was not just faster; it was a different category of technology that path dependence had delayed by decades.