Magnetic tape
A breakthrough storage medium draws inspiration from a vacuum cleaner
An early magnetic tape machine

An innovation inspired by an ordinary vacuum cleaner wound up being the key to a new generation of data storage technology: magnetic tape. Beginning in the early 1950s, magnetic tape greatly increased the speed of data processing and eliminated the need for massive stacks of punched cards as a data storage medium.

In the early 1950s, IBM, Remington Rand and several other companies were working on the first commercial electronic computers that used vacuum tubes instead of the mechanical switches found on tabulating machines. The processors in these machines ran so fast that computer memory and punched card storage could not keep up. Computers were generating massive amounts of data, which needed to be stored and retrieved more quickly and efficiently. The race to develop a faster, higher-density storage medium was on.

Magnetic tape storage had already shown its usefulness in the audio recording industry. German engineers in the 1930s perfected steel magnetic tape, and IBM engineers were experimenting with magnetic-coated plastic tape in the 1940s, intending to use it for data storage and retrieval. In the early 1950s, the first general-purpose digital computer for business, UNIVAC, employed a heavy metallic tape for storage, but plastic tape was far cheaper and lighter. Any company that could use it to develop a new standard would have a good chance of commanding the next wave of electronic computing.

An engineering challenge

IBM engineers encountered a problem with using large tape reels to store data: the thin tape had to be capable of starting and stopping at high speeds without breaking. Mechanical engineer James A. Weidenhammer and a team of six engineers were tasked with solving the problem and developing a robust high-speed drive.

“We had no clear idea of which approach to take,” Weidenhammer said. “Very fast starts and stops were desirable to minimize the wasted tape and read-write delays. But with tape speeds anticipated to be 100 to 200 inches per second, it was obviously impractical to accelerate bulky tape storage reels rapidly enough. Storage loops or buffers would be necessary in the tape path for gradual acceleration of the reels.”

The buffer loops in the magnetic tape became the team’s focal point. If engineers could find a way to maintain a sufficiently large U-shaped loop, the tape could be started and stopped at very high speeds without breaking it. 

The buffer loops in the magnetic tape became the team’s focal point
An unlikely breakthrough
A vacuum cleaner and baby pants

Weidenhammer’s team experimented with a combination of idler arms and pulleys, block and tackle arrangements, and various air pressure schemes to form a buffer loop of tape, but none worked adequately. Then the team turned to an unlikely tool: an ordinary vacuum cleaner.

At first, they used the vacuum to blow air into a rectangular column to push the tape down to form a loop, but that didn’t work well. So they reversed course, using the vacuum to suck the loop from the bottom of the column. The vacuum held the tape loop in place and reduced damaging air resistance that could tear the tape. It worked.

Anxious to try the new concept but lacking material to create a vacuum column, Weidenhammer sent a young assistant, engineer Jack Seely, to the nearest drugstore to buy a pair of baby pants to use as a membrane. The thin, flexible material acted as a crude valve allowing air to flow out faster than it came in, creating a partial vacuum.

Magnetic tape dominates for decades
1953

IBM introduced the tape drive vacuum column for use with the IBM 701 Electronic Data Processing Machine. The invention broke the memory and storage logjam, and the vacuum column became an industry standard that IBM and other manufacturers used for several decades.

1964

Tape storage capacity increased rapidly. When the IBM System/360 was introduced in 1964, IBM offered vacuum column magnetic tape drives that could process 90,000 characters per second and start and stop in just 0.0015 second. For more than 30 years, magnetic tape dominated offline storage and data transfer. Large magnetic reels spinning in rapid, back-and-forth bursts became a cultural icon. Stock shots of tape drives in motion were widely used to represent computers in movies and television.

1984

By the 1980s, reels of magnetic tape began to give way to more compact and higher-density storage technologies such as cartridge-based tapes. In 1984, IBM discontinued reel-to-reel products, replacing them with tape cartridges beginning with its introduction of the cartridge-based 3480 family. Magnetic tape remains viable in modern data centers for data backup because tape endures as a very cost-effective, flexible and scalable medium for high-capacity storage.

While magnetic tape has been largely replaced in consumer environments by other storage media, like hard disk drives, solid-state disk drives and cloud computing, modern business systems still often rely on magnetic tape as a low-cost, durable form of data backup. It is cheap, quick to read, and can securely retain data for 30 years or more.

Which is to say, magnetic tape isn’t going away any time soon. IBM remains committed to the technology in hybrid cloud environments. With worldwide data expected to hit 175 zettabytes by 2025 — representing 61% annual growth — the company believes magnetic tape will power hybrid cloud environments for decades to come. And IBM researchers continue to find new ways to push storage density. In late 2020, the company announced that, in collaboration with Fujifilm, it had achieved 317 gigabits per square inch in aerial density. That’s 27 times the density of state-of-the-art commercial tape drives.

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