First Hard Disk Drive
IBM shipped the 350 Disk File, the first commercial hard disk drive, storing 5 MB
September 13, 1956
IBM's Spinning Revolution
On September 13, 1956, IBM introduced the IBM 350 Disk Storage Unit, the world's first hard disk drive, as a component of the IBM 305 RAMAC computer system. RAMAC stood for Random Access Method of Accounting and Control. The 350 could store five megabytes of data on 50 aluminum disks, each 24 inches in diameter, spinning at 1,200 RPM. The entire unit was the size of two refrigerators and weighed over a ton. IBM leased the 305 RAMAC for approximately $3,200 per month. Despite its enormous size and cost, it represented a fundamental breakthrough: data could now be accessed randomly, from any location on the disk, rather than having to be read sequentially from magnetic tape.
Why Random Access Changed Everything
Before hard disk drives, businesses stored data on magnetic tape, which worked similarly to audio cassettes. To find a specific piece of information, the computer had to read through the tape from the beginning until it reached the right spot. This sequential access was slow and cumbersome for applications that needed to jump between records constantly, such as airline reservation systems or bank accounts. The IBM 350's ability to access any record in under a second, regardless of where it was stored, made entirely new kinds of computing applications practical. Airlines were among the first major customers, using RAMAC to manage reservation data in real time.
From a Ton of Storage to Your Pocket
The evolution of hard disk technology over the following seven decades is extraordinary. By 1980, the 5.25-inch hard drive had brought storage into personal computers. By the early 2000s, drives could hold hundreds of gigabytes. Today, a single 3.5-inch hard drive can store over 20 terabytes of data, millions of times more than the original IBM 350. Solid-state drives have increasingly replaced spinning disks in laptops and phones, storing vast amounts of data on chips with no moving parts. The smartphone in your pocket holds more data than a room full of 1956 RAMAC machines could have stored, and accesses it in a fraction of a millisecond.