What is Tape Storage?

In an era defined by artificial intelligence, big data, and the relentless generation of information, it might seem surprising that one of the most important data storage technologies is one that has been around for over seventy years. Magnetic tape storage, a technology first commercialised in the early 1950s, is not only surviving but thriving as a critical component of modern enterprise and hyperscale data centres.

Far from being a relic of the past, tape storage is experiencing a resurgence. In 2024, a record 176.5 exabytes of compressed tape capacity were shipped, marking the fourth consecutive year of growth. This renaissance is driven by a perfect storm of factors: the exponential growth of data, the increasing cost of disk and flash storage, the need for robust cybersecurity against ransomware, and the sheer economic and environmental advantages that tape provides.

At its core, a tape storage system is comprised of three fundamental components: tape cartridges, tape drives, and tape libraries.

The Three Pillars of a Tape System

1. Tape Cartridges (The Media): These are the physical plastic cassettes that hold the magnetic tape. They are the storage medium itself. Modern cartridges are highly sophisticated, containing a long, thin strip of magnetic film coated with a specialised material like barium ferrite. The primary standard for tape media today is Linear Tape-Open (LTO), developed and maintained by a consortium of companies including IBM, HPE, and Quantum. Each generation of LTO roughly doubles the capacity of its predecessor. The current generation, LTO-10, can hold 30 terabytes (TB) of native (uncompressed) data, or up to 75 TB with compression. For organisations with less demanding capacity needs, the previous generation, LTO-9, remains a cost-effective workhorse, offering 18 TB native capacity at roughly £5 per terabyte.
2. Tape Drives (devices that read and write): The tape drive is the device that reads data from and writes data to a tape cartridge. This is a highly sophisticated piece of machinery. The drive uses advanced read/write heads to access the data on the tape as it spools at high speeds. A critical characteristic of tape is that it is a sequential access medium. This means that to read a specific piece of data, the drive must fast-forward or rewind the tape to the correct location, much like a VHS tape. This is in contrast to hard disk drives (HDDs) or solid-state drives (SSDs), which offer random access and can retrieve any piece of data almost instantly. For this reason, tape is not suited for active, frequently accessed data. However, modern LTO-10 drives can achieve a native data transfer rate of 400 MB per second, which is faster than many consumer-grade hard drives and does not diminish as the tape fills up. The drives themselves are expensive—costing thousands of pounds which is a primary reason why tape is generally not a practical solution for home users.
3. Tape Libraries (automated media handling): A tape library, sometimes called a tape silo, is a robotic system that houses hundreds or even thousands of tape cartridges and multiple tape drives. It automates the process of selecting, loading, and unloading cartridges. The library uses a robotic arm (or "picker") to move a cartridge from its storage slot and insert it into an available tape drive, at which point the data can be read or written. This automation allows for massive, unattended storage operations. A single large library can store over 100 petabytes (PB) of data. Companies like IBM and Spectra Logic are the primary manufacturers of these large-scale libraries and smaller libraries exist from companies like Qualstar.

The Modern Value Proposition: Cost, Security, and Longevity

The revival of tape is not about nostalgia; it is a strategic, data-driven decision by the world's largest data consumers, including hyperscalers like AWS, Google, and Microsoft. Tape offers a unique set of advantages that make it indispensable.

Cost-Effectiveness: Tape is the undisputed champion when it comes to the cost per terabyte. For long-term data retention, the total cost of ownership of tape can be 80% lower than spinning disk and often an order of magnitude lower than active cloud storage. The LTO Program's own roadmap envisions cartridges with capacities up to 576 TB native (and 1.44 PB compressed) with LTO-14, promising to make tape even more cost-efficient in the future. This is particularly important as the enterprise storage market faces price hikes, with 30TB HDDs reportedly increasing from £3,00 to £1,000 in just one year. For organisations, moving infrequently accessed "cold" data can constitute up to 70-80% of all enterprise data—to tape makes overwhelming economic sense.

Unmatched Security and Cyber Resilience: In a world of escalating ransomware attacks, tape provides an unparalleled security advantage: an air gap. An air-gapped backup is a copy of data that is completely offline and inaccessible to a network. A tape cartridge stored securely on a shelf or in a vault is immune to malware, including ransomware, which cannot encrypt files it cannot reach. This makes tape a critical last line of defence in a "3-2-1" backup strategy (three copies of data, on two different media, with one copy stored offsite). LTO also offers features like Write-Once, Read-Many (WORM), which further protects against data being overwritten or tampered with.

Energy Efficiency and Longevity: Unlike HDDs and SSDs, which require constant power to keep data accessible, a tape cartridge consumes zero energy when not being read or written. This makes it an incredibly sustainable storage option, a factor that is becoming increasingly important as data centres grapple with their energy footprint and sustainability goals. Furthermore, tape has an impressive lifespan. Under proper storage conditions—stable temperature and humidity—a tape cartridge can reliably preserve data for 30 years or more, making it an excellent medium for long-term archival.

Who Uses Tape and Why?

The use cases for tape are far more diverse than its "backup-only" reputation suggests.

- Scientific Research: CERN, the European Organisation for Nuclear Research, is one of the world's largest tape users, relying on it to store over 1.2 exabytes of physics data generated by the Large Hadron Collider. This data is critical for future analysis and must be preserved for decades.

- Media and Entertainment: Major film studios and production houses use tape to archive their massive raw footage, finished films, and audio assets. A single feature film can generate petabytes of data that must be securely preserved "forever".

- Finance and Healthcare: These sectors generate vast amounts of transactional, patient, and compliance data that must be retained for years or even decades. Tape provides a secure, immutable, and cost-effective way to meet these stringent regulatory requirements.

- AI and Machine Learning: The AI boom is a major driver of tape's growth. Training large language models (LLMs) requires massive datasets. While this data is expensive to store on high-performance flash or disk, it is ideally suited for tape when not in active use. Organisations are using tape to build vast and affordable data lakes, preserving raw data for future model retraining and iterative learning processes.

Conclusion

Tape storage is a classic example of a mature technology that has continuously evolved to solve new problems. While it may not be the right tool for storing active, transactional data, its unique combination of low cost, high capacity, inherent security, and long lifespan makes it the perfect solution for the data that most of the digital world has generated but needs to keep. As the world creates more data, and as the need for cyber-resilient, sustainable storage grows, the role of tape storage that’s 70 years old and counting has never been more relevant.

Smarter,  strategic thinking.