Magnetic tape has been used for data storage and backup since the 1950s. It continues to be an important medium for data archiving and backup today due to its low cost, high data density, longevity, and portability. Some key uses of magnetic tape include:
Data Backup
One of the most common uses of magnetic tape is for data backup. Tape drives and robotic tape libraries are used to backup critical data from hard disk drives in data centers and enterprise environments. Tape provides an offline, removable and portable backup medium that can be easily taken offsite for protection against disasters. Tape cartridges store large amounts of data at a low cost compared to hard disk drives. The Linear Tape-Open (LTO) format provides up to 30 TB of uncompressed capacity per cartridge.
Archiving
Magnetic tape is ideal for long-term archiving of data that does not need frequent access but still needs to be retained. Its portability, longevity and low cost make it well-suited for archiving data for regulatory compliance, financial records, medical imaging, scientific data and more. Tape cartridges can be stored offline in protected environments and last for decades. LTO tape drives provide backwards compatibility to read older tapes.
Big Data and HPC
The massive amounts of data generated by big data analytics, high-performance computing (HPC) and hyperscale cloud applications is often first captured and staged on tape. The high capacity and data transfer speeds of modern tape drives allow them to keep pace with large scale data generation. After capture, subsets of data can be processed and migrated to disk for faster analysis. When processing is done, remaining data can be returned to tape.
Media and Entertainment
The media and entertainment industry relies heavily on magnetic tape for video production and broadcasting. Recording studios use tape for master audio recordings. Video tapes are used for storage, editing and playback of footage and programs. Data tape cartridges store content for film, TV and music production. Tape’s portability enables content to be easily transported and shared.
Cold Storage
Many organizations use magnetic tape as a cold storage tier within a storage hierarchy. Less frequently accessed data can be migrated from disk to tape for cost-effective long term retention. When data on tape is needed, it can be recalled back to disk. This practice frees up expensive disk for more performant uses while still retaining massive amounts of rarely used data.
History of Magnetic Tape
Magnetic tape technology was first developed in Germany in the 1920s for audio recording. The first tape recorders were introduced in the 1940s. In 1951, UNIVAC developed the first commercial computer tape drive for use with its mainframe computers. IBM launched its first commercial tape drive, the IBM 726, in 1952.
During the 1960s and 1970s, open reel tapes were widely used for data storage on mainframe systems and early supercomputers. In the late 1970s, tape formats miniaturized into cassettes and cartridges, such as the Digital Linear Tape (DLT) and Linear Tape-Open (LTO) formats that are still used today.
As disk storage advanced in the 1980s and 1990s, tape usage focused more on backup and archiving roles. However, the need for affordable high-capacity storage led tape technology to continue advancing. LTO tape drive capacity and performance have steadily grown over multiple generations since the LTO standard was introduced in 2000.
Key Milestones
- 1928 – Fritz Pfleumer develops the first magnetic tape using iron oxide powder on strips of paper tape
- 1947 – First commercial tape drive, the Model A, released by Ampex
- 1951 – UNIVAC develops the UNISERVO tape drive for use with mainframe computers
- 1952 – IBM releases the IBM 726 tape drive for the IBM 701 computer
- 1960s/70s – 9 track open reel tapes widely used on mainframes
- 1979 – Digital Linear Tape (DLT) format developed by DEC
- 1989 – Digital Data Storage (DDS) tape format introduced by Sony and HP
- 1997 – Linear Tape-Open (LTO) format specification released by IBM, HP and Seagate
- 2000 – First LTO1 tape drive launched with 100 GB capacity
- 2020 – LTO-9 launched providing 18 TB native capacity
How Magnetic Tape Works
Magnetic tape stores data on thin strips of plastic tape that are coated with magnetic material. Most modern tapes use barium ferrite (BaFe) particles as the magnetic medium.
Data is stored by magnetizing particles on the tape surface to represent bits – a magnetized spot is a 1, no magnetization is a 0. The presence or absence of magnetic fields is detected as the tape moves over read/write heads to access the data.
Key Components
- Tape – Polyester tape with magnetic coating that provides the data storage medium
- Read/Write Heads – Convert electrical signals to magnetic fields to write data, and vice versa to read data
- Motors – Precisely control tape movement over heads for read/write operations
- Sensors – Optical and magnetic sensors to track exact tape positioning
Modern tape drives use serpentine recording where tracks are written diagonally across the tape to increase capacity and performance. Multiple parallel channels allow interleaved access to data across the tape width.
Data Recording
To write data, an electrical current flows through the write head, generating a magnetic field that magnetizes particles on the tape surface as it moves over the head. The pattern of magnetized/non-magnetized particles represents the binary data.
Data Reading
During readback, the magnetic fields on the tape induce an electrical signal in the read head. This analog signal is then amplified and converted to digital data.
Linear versus Helical Recording
Most modern tape drives use linear recording where tracks run lengthwise along the tape. Some formats like DVCAM use helical scan where tracks are recorded diagonally in a helix pattern for higher data density.
Tape Generations and Formats
There are a number of different magnetic tape formats that have evolved and been used over time:
Open Reel Tapes
Early mainframe systems used large open reel tapes up to 10.5 inches wide. Different densities and track layouts were used including 7 track, 9 track, etc. Common reel sizes ranged from 10.5″ to 2″ wide.
Cassette Tapes
Smaller cassettes house tape on hubs or reels and contain less tape. Formats include Compact Cassette and the Digital Data Storage (DDS/DAT) cassettes used for backup.
Cartridge Tapes
These completely enclose the tape reels and have higher capacity than cassettes. Examples include Linear Tape-Open (LTO), IBM 3592 and Oracle T10000 tape cartridges.
Tape Capacity
Tape capacities have grown tremendously over the decades:
- 1950s – Open reel tapes stored up to 30 MB
- 1980s – DDS could store up to 10 GB
- 1990s – DLT could store 35 GB
- 2000s – LTO-1 stored 100 GB per cartridge
- 2010s – LTO-5 held 1.5 TB
- Today – LTO-9 holds 18 TB native and 45 TB compressed per cartridge
Modern Tape Drive Technology
Modern tape drives deliver high capacity storage combined with fast data transfer speeds using a variety of technologies:
High-Speed Interfaces
Tape drives now utilize high speed host interfaces like Fibre Channel and SAS to enable data transfer rates up to 300 MB/sec.
Serpentine Recording
Also called linear serpentine recording, this technique writes tracks diagonally across the tape to increase density. Tape motion alternates direction after each diagonally written track.
Multi-Channel Architecture
Multiple read/write channels allow interleaved access across the width of the tape for performance scaling. Current LTO-9 drives use 32 data channels.
Helical-Scan Recording
Used in formats like DVCAM and DVCPRO, helical-scan writing wraps tracks diagonally around the tape reels to increase density. The tape wraps around a rotating drum.
Thinner Tape
Thinner tape allows more tape to be contained in a cartridge spool. Modern tape is 4-6 micrometers thick compared to the 12 micrometers of early tape.
Choosing a Tape Format
When selecting a tape storage solution, key factors to consider include:
- Capacity – Required storage density and scalability
- Performance – Throughput speed for backup windows and restores
- Automation – Platforms for automated libraries
- Durability – Shelf life and environmental tolerances
- Cost – Acquisition cost and TCO
- Roadmap – Format direction and development
Popular current tape formats include:
LTO (Linear Tape Open)
LTO is one of the most widely used tape standards, leveraging linear serpentine recording. It is popular for mid-range and enterprise backup and archiving. Current LTO-9 tapes hold 18 TB native and have a raw data rate of 400 MB/sec.
IBM 3592
The 3592 format developed by IBM uses jagged recording across multiple parallel tracks for high capacity and performance. Drive models are available with native capacities up to 15 TB.
Oracle T10000
Oracle’s T10000 drives provide high capacity storage with transfer speeds reaching 400 MB/sec in some models. Capacities scale up to 10 TB native currently.
Quantum LTO
Along with IBM and Fujifilm, Quantum is one of the three current LTO Consortium members that manufacture LTO tape drives and media. Their portfolio includes LTO-8 and LTO-9 options.
Tape Libraries and Automation
While standalone tape drives are still used today, most enterprises take advantage of automated tape libraries for efficient backup operations and archive management. Tape libraries include:
- Cartridge slots – Storage slots for tape cartridges
- Machine gripper – Robotic mechanism to move cartridges
- Barcode reader – Scans cartridge labels for inventory
- Tape drives – One or more tape drive read/write devices
- Import/export slots – To add or remove tapes from library
Key benefits of automating tape storage in libraries include:
- Faster backup and recovery processes
- Efficient media management and monitoring
- High slot density to minimize physical footprint
- Scalability to accommodate growth
From small autoloaders to massive robotic silos holding thousands of slots, automated libraries enable tape storage resources to be shared across a data center.
Tape Use Cases
Some examples of practical use cases for tape storage include:
Backup
Tape is ideal as a backup destination for periodic full and incremental backups from disk. Tape cartridges can be rotated offsite for protection.
Archive
Regulatory compliance and legal hold often mandate data retention for years. Tape provides affordable large-scale archiving.
Big Data
Tape staging speed allows massive data sets from scientific research, medical imaging, geospatial and other big data sources to be saved initially.
Cloud Archives
Hyperscale cloud providers may use tape as part of storage hierarchies for low-cost, high-capacity data retention.
Media Content
The entertainment industry relies on tape for video production, editing and archival of content.
Virtual Tape Libraries
Disk-based virtual tape libraries emulate the behavior of physical tape for backup operations.
| Use Case | Tape Benefits |
|---|---|
| Backup | Removable, portable, offline, durable |
| Archive | High capacity, low cost, long lifespan |
| Big Data | High throughput, scalability |
| Media Content | High bandwidth, simplicity, portability |
Tape Storage Challenges
While tape retains many advantages, there are some challenges to consider:
- Access latency – Slow data access compared to disk or flash
- File management – No in-place updates or deletions, files need rewriting
- Durability – Media must be stored properly to ensure longevity
- Cost – Drives, media and automation require upfront investment
Solutions exist to mitigate most limitations. For example, disk cache stages data and virtual tape libraries improve access times. Proper environmental controls preserve archived tapes. Overall, the vast economies of scale from tape make it highly cost-effective for backup and archival applications.
The Future of Tape Storage
Tape storage has retained an indispensable role in the data center for decades by providing the lowest cost per GB, energy efficiency and storage density. This is likely to continue with massive growth in data driving continued tape evolution:
- Capacity and performance will increase with newer LTO generations
- New media coatings and track styles could boost tape density
- Scaling to hundreds of terabytes per cartridge may be possible
- Shingled magnetic recording will likely be adopted
- New optical and hybrid optical/magnetic tapes could emerge
Demand for tape storage shows no signs of abating, especially with explosive enterprise data growth and new big data sources. Tape’s unmatched cost economics will ensure it remains a pivotal component of data center storage architectures for the foreseeable future.
Conclusion
For over half a century, magnetic tape has served as the most cost-effective medium for backup, archival and other secondary storage applications. Tape continues to evolve with new standards like LTO pushing capacity, performance and areal density higher each generation. With long-term scalability, energy efficiency, affordability and ease of use, magnetic tape is likely to remain critical for data centers well into the future despite increasing competition from other media like disk, flash and cloud storage. Careful evaluation of use cases, requirements and available tape technologies allows selecting the optimal tape storage solution.
