How Is Data Stored on Tape? Magnetic Tape Storage Explained
Tape might seem old-fashioned, but a single modern cartridge can hold more data than a stack of hard drives. Cloud providers, banks, and research labs still trust it with their most important long-term archives.
So how does a strip of plastic film store tens of terabytes? This guide explains how data is stored on tape, how tape drives read and write it, and why tape is still one of the safest places to keep data for decades.
Quick answer: Data is stored on tape by magnetizing tiny particles in a coating on a thin plastic film. A tape drive’s write head flips the magnetic direction of these particles to record 1s and 0s in thousands of narrow parallel tracks. Modern LTO and IBM 3592 drives write tracks back and forth along the tape in a serpentine pattern, and read them back with a read head that senses the magnetic changes.
What Is Magnetic Tape Storage?
Magnetic tape is a long, thin strip of plastic film coated with magnetic particles, wound on a reel inside a cartridge. In enterprise IT, the two main formats are:
- LTO (Linear Tape-Open): The open industry standard used by most businesses
- IBM 3592: IBM’s enterprise tape format, used in large IBM tape libraries
Tape is used mainly for backups, archives, and data that must be kept for years but is rarely accessed.
How Does Tape Store Data?
The Magnetic Coating
The tape is coated with extremely small magnetic particles. Modern LTO generations use barium ferrite (BaFe) particles, which are very stable and allow data to be packed tightly.
Recording 1s and 0s
Each tiny area of the tape can be magnetized in one of two directions. The drive uses changes in magnetic direction to represent binary data: the 1s and 0s that make up every file.
The Write and Read Heads
As tape moves past the drive head at high speed:
- The write head creates a magnetic field that sets the direction of the particles beneath it.
- The read head senses those magnetic changes and turns them back into data.
Modern drives read data right after writing it to verify it was recorded correctly.
Linear Serpentine Recording
LTO and 3592 drives use linear serpentine recording. The drive writes a set of tracks down the full length of the tape, then reverses direction and writes the next set on the way back. It repeats this many times, building up thousands of tracks across the width of the tape.
Older formats like DAT and AIT used helical scan recording, where a spinning drum wrote diagonal stripes. That method is mostly obsolete in enterprise storage today.
How Data Is Accessed on Tape
Tape is a sequential access medium. Unlike a hard drive, it cannot jump straight to a file. The drive has to wind the tape to the right spot first, which can take a minute or more.
That is why tape is best for data you rarely need to read. It is also why tools like LTFS (Linear Tape File System) were created. LTFS lets a tape appear like a drive with folders and files, which makes tape easier to use for archives and media workflows.
Inside a Tape Drive
When you load a cartridge, the drive:
- Pulls the tape leader out of the cartridge and threads it onto a take-up reel
- Aligns the head with the correct data tracks using servo tracks written at the factory
- Reads or writes data, applying compression, error correction, and encryption if enabled
- Updates a small memory chip in the LTO cartridge that stores usage and index information
Keeping the head clean is part of normal drive care. See our guide on how to use an LTO cleaning tape.
Common Tape Formats and Capacities
According to the LTO Program, current capacities include:
| Format | Native Capacity | Compressed (2.5:1) |
| LTO-8 | 12TB | 30TB |
| LTO-9 | 18TB | 45TB |
| LTO-10 | 30TB or 40TB | 75TB or 100TB |
IBM’s IBM 3592 JF cartridge holds up to 50TB native with a TS1170 drive.
One key change: LTO-10 drives cannot read or write older LTO cartridges. Earlier generations could typically read one or two generations back. Plan migrations before you retire older drives.
Why Tape Is Still Relevant
- Lowest cost per terabyte for long-term storage
- Long life: 30 years or more when stored properly
- Air gap: Offline tapes cannot be reached by ransomware
- Low power: No electricity used while sitting on a shelf
- WORM options: Write-once cartridges support compliance rules
- Encryption: Hardware AES-256 encryption in modern drives
Curious who relies on tape today? Read who still uses tape storage.
How Long Does Data Last on Tape?
Tape can hold data for 30 years or more in the right conditions. Store tapes in a cool, dry, stable room, away from dust, sunlight, and magnetic fields. Follow the temperature and humidity ranges your media vendor recommends.
Can You Sell Used Data Tapes?
Yes. Used LTO and 3592 cartridges often have resale value, especially recent generations such as LTO-9 tapes and new or lightly used stock.
When you sell your used tape media to We Buy Used IT Equipment:
- Send your list: Generation, quantity, and condition
- Get a quote based on current market demand
- Ship securely with tracked logistics
- We sanitize every tape to NIST 800-88 standards and send a certificate of data destruction
- Get paid once your tapes are received and processed
Final Thoughts
Data is stored on tape by magnetizing tiny particles in thousands of narrow tracks, written back and forth along the length of the tape. That simple idea, refined over decades, gives tape huge capacity, long life, and a real air gap.
Have used LTO or 3592 tapes after a migration? Get a fast quote from We Buy Used IT Equipment and turn surplus media into cash.
Frequently Asked Questions
How does magnetic tape store data?
Tape stores data by magnetizing tiny particles in a coating on a thin plastic film. The drive’s write head sets the magnetic direction of each small area to represent 1s and 0s, and the read head senses those changes to read the data back.
What is linear serpentine recording?
It is the method LTO and IBM 3592 drives use to write data. The drive writes tracks along the full length of the tape, then reverses and writes more tracks on the way back, repeating until thousands of tracks fill the tape.
How much data can an LTO tape hold?
LTO-9 holds 18TB native or 45TB compressed. LTO-10 holds 30TB or 40TB native, or 75TB to 100TB compressed at a 2.5:1 ratio. IBM 3592 JF cartridges hold up to 50TB native.
How long does data last on magnetic tape?
When stored in a cool, dry, stable environment, data on modern tape can last 30 years or more, which is longer than typical hard drives or SSDs.
Is my data safe if I sell my used tapes?
Yes, when you sell to We Buy Used IT Equipment. Every cartridge is sanitized to NIST 800-88 standards, tracked through chain of custody, and documented with a certificate of data destruction.
