Magnetic tape has been used for data storage and backup since the 1950s. For decades, it was considered the primary medium for archiving important data that needed to be saved indefinitely. However, recent developments have called into question whether magnetic tape truly provides permanent storage.
What is magnetic tape?
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany during World War II for recording radio broadcasts and speeches. After the war, it was adopted for use in early computers to store data and programs.
Data is recorded on magnetic tape by magnetizing tiny iron oxide particles embedded in the tape’s coating in patterns representing binary digits (bits). The magnetized patterns representing the data can be read back and converted into electrical signals by a tape drive head.
Because magnetic tape allows for sequential access (i.e. data can only be read or written sequentially from start to end), it is well suited for backup, archival, and data transfer applications. Tape drives can access data on tape far more rapidly than accessing data directly off disks.
Advantages of Magnetic Tape
There are several key advantages that made magnetic tape the dominant medium for data archiving for decades:
- High capacity: Modern tape cartridges can store tens of terabytes of compressed data, providing very high storage density.
- Longevity: Magnetic tape has a long history of reliability for long-term storage measured in decades.
- Portability: Tape cartridges are small, light, and durable, making them easy to transport and store offsite.
- Low cost: The cost per gigabyte of storage is very low compared to hard disks.
- Sequential access: Data is stored sequentially allowing for high-speed streaming reads and writes.
These advantages made tape ideal for offline storage and data backup. Tape was perceived as more robust and reliable than other media like optical discs for achieving decades of archival storage.
Is data on magnetic tape permanent?
For many years, magnetic tape was considered a permanent archival medium. It was thought that if tapes were stored under proper environmental conditions, the data could persist unchanged for 30 years or more.
However, in recent years, some studies have challenged the perception of permanent storage on magnetic tape:
- Researchers at the Lawrence Berkeley National Laboratory conducted accelerated aging tests on magnetic tape and found that signals degraded significantly in as little as 10 years under normal storage conditions.
- The National Institute of Standards and Technology found bit error rates increased and data could be lost in tape archives after only 2 years of use.
- A large-scale study by the University of Toronto found that data on tape deteriorates rapidly due to four key factors: hydrolysis, oxidation, magnetization loss, and binder breakdown.
These findings suggest magnetic tape does naturally degrade over time, putting archival data at risk. The main mechanisms causing data loss on tape include:
Hydrolysis
This is the breakdown of the polyester bonding that holds the magnetic particles to the tape. It causes the tape to become brittle and layers to separate.
Oxidation
Oxidation occurs when iron oxide particles on the tape are exposed to moisture or high temperatures. It corrodes the magnetic material and causes data loss.
Binder breakdown
Over time, the binders that hold magnetic particles to the tape degrade. Binder breakdown causes the magnetic material to detach and fall off.
Magnetization loss
This is when the magnetic strength of the particles fades, leading to weak signal output. Demagnetization can occur due to exposure to magnetic fields.
These degradation factors mean tape may only be reliable for storing data for 10-30 years, not centuries or indefinite periods.
Does proper storage increase tape life?
Proper storage conditions can help maximize the lifespan of magnetic tape. Ideal conditions involve:
- Cool temperatures between 18-24°C. Heat accelerates binder breakdown and demagnetization.
- Low humidity below 40%. High moisture damages tape through hydrolysis.
- Dust-free environment. Dust can scratch tape surfaces causing errors.
- No direct sunlight or UV exposure. Sunlight can fade and warp tape.
- Enclosed in protective cases. Casing prevents physical damage and demagnetization.
- Stored vertically rather than horizontally.
- Periodic rewinding to avoid slack and stuck tape layers.
Maintaining proper archival conditions can potentially extend tape life to the 30-100 year range. However, deterioration factors cannot be eliminated completely.
What are the alternatives for long-term data archiving?
Given the realization that magnetic tape may not offer truly permanent storage, what other media options exist for long-term archival of important data that must be preserved indefinitely?
Hard disk drives
HDDs are reliable for everyday storage and backups, but mechanical components give them a limited lifespan around 5 years. Not ideal for long-term data retention.
Solid state drives
SSDs lack moving parts so avoid mechanical failures. Estimated lifespan is 10-20 years. More expensive per GB than HDDs.
Optical discs (CDs, DVDs, Blu-ray)
CDs and DVDs have lifespan around 10 years. Blu-ray discs are more stable chemically but still vulnerable to scratching. Regular integrity checks needed.
Cloud storage
Storing data redundantly in multiple data centers provides protection against hardware failures. But there are risks around vendor lock-in and financial stability.
Offline storage arrays
Network-attached devices with multiple HDDs or SSDs can offer data protection through RAID. But hardware still has limited lifespan.
Magnetic tape
Still one of the most cost-effective solutions for mass data archiving if stored properly. But requires active rewinding, refreshing, and migration every 5-10 years as technology changes.
Is periodic migration the best practice?
Given the risks posed to archived data by both natural deterioration and technology obsolescence, many experts recommend periodic migration to new media. This involves:
- Rewinding and validating all tapes every 2-5 years.
- Checking for uncorrectable errors indicating physical degradation.
- Transferring data to new tapes every 5-10 years before significant deterioration begins.
- Migrating data to new storage technologies as they emerge.
- Keeping old tapes as backups in case new media also degrades.
Regular migration to the latest storage technologies preserves not just the data itself, but the accessibility and usability of the data. However, it requires continued investment in media renewal and data management resources.
Does reformatting help preserve magnetic tapes?
Reformatting (sometimes called refreshing or repackaging) involves reading the data off old tapes and writing it to new tapes. This can potentially help extend the life of archived data in several ways:
- Detect and correct any unrecoverable read errors.
- Reset the duty cycle by writing to brand new tape.
- Update to the latest tape technology for better capacity and density.
- Discard any tapes showing deterioration.
- Apply improved error correction codes to better protect data.
Industry best practices suggest repackaging tape-based data at least every 10 years to avoid media deterioration issues. More frequent refreshing may be warranted for at-risk or highly valuable data. But it’s still just a stopgap measure, not a path to permanent storage.
What about tape backup versus archiving?
It’s important to distinguish tape-based backup from long-term archiving. Weekly or daily backups to tape facilitate data recovery and business continuity should primary storage fail. But these backup tapes are overwritten frequently and not intended for permanent data retention.
Archival tapes contain historical records or other data that must be preserved indefinitely. These write-once tapes are stored offline under specialized conditions. Periodic repackaging is needed to preserve accessibility of the data as technology changes.
In short, regular backup tapes and long-term archival tapes have fundamentally different use cases and maintenance requirements.
Does permanent storage exist?
No storage medium yet devised can provide truly permanent data storage. All technologies have finite lifespans and limitations:
- Magnetic media: Deteriorates over decades due to material breakdown.
- Optical discs: Can delaminate, oxidize, or become unreadable.
- Hard drives: Mechanical failure inevitable over time.
- Solid state drives: Electron leakage and data corruption still occur.
- Paper: Yellows, becomes brittle, and degrades over centuries.
- Microfilm: Requires specialized readers and storage; limited capacity.
No existing digital or analog medium provides true lifetime persistence. Achieving a closest approximation requires an active archive strategy:
- Media redundancy across multiple technologies.
- Geographic distribution of archive copies.
- Ongoing data validation and refreshing.
- Retention of legacy reading systems.
- Periodic migration to new technologies.
But ultimately, lifetime data preservation will likely require fundamental advances in data storage materials and systems.
What future technologies could provide permanent storage?
Several emerging technologies aim to provide near-permanent data storage:
DNA storage
Using synthetic DNA as a data storage medium leverages billions of years of evolution for preservation. DNA can endure for centuries when kept cold and dry. However, it currently has very high costs and slow read/write times.
Glass discs
Writing data into fused quartz glass using femtosecond lasers creates extremely stable and long-lived data storage. But glass discs are currently very expensive to produce.
M-DISCs
M-DISC uses specially treated inorganic material written by a different kind of laser. Testing shows it may last hundreds of years with minimal degradation. But adoption has been limited so far.
Perovskite crystals
Encoding data in perovskite crystal sheets has potential for cheap, dense and stable room temperature storage lasting centuries. But development is still at early stages.
While promising, all these technologies are far from mass adoption. Extensive testing over decades is still required to confirm their longevity advantages over magnetic tape.
Should magnetic tape be used for archiving?
Magnetic tape remains a cost-effective solution for long-term data archiving, but it requires an active management strategy:
- Validate tape health and readability every 2-5 years.
- Migrate data to new tapes before degradation starts.
- Store multiple copies in different locations.
- Replace damaged tapes.
- Keep legacy equipment to read old formats.
With proper care and maintenance, magnetic tape archives can reliably preserve data for 20-50 years. For truly permanent data retention, emerging technologies like DNA storage show promise once technical hurdles are overcome.
Conclusion
Magnetic tape remains a popular choice for long-term data archiving due to its high capacity, low cost, and portability. However, deterioration factors limit tape’s lifespan for permanent data storage to a few decades at most. Achieving indefinite data preservation requires actively managing a tape archive, along with periodic migration to the latest storage technologies. Other media like optical discs also degrade over time. Truly permanent digital storage may need to wait for disruptive new technologies like DNA- or crystal-based systems currently under development.
