Media

Clearing out backup tapes (LTO, DAT) after archive closure

16 January 2026 · 7 min read · DeSnipperaar

Many IT departments have a cupboard with archive equipment from an earlier era. LTO-4, LTO-5, occasionally still DAT or DLT, often in silent cartridge trays. The backup strategy migrated to the cloud or to modern disk-based solutions long ago, but the old tapes are still there. Nobody dares to throw them out while it is unclear what is on them, and nobody dares to read them back while it is unclear whether the drives still work. This article helps you cut that knot.

Theme: physical destruction of magnetic tapes, with guidance from NIST 800-88 and DIN 66399.

Why tapes are different from drives

Tapes store data on a thin magnetic layer on a plastic ribbon. An LTO-8 cartridge contains nearly a kilometre of tape per cartridge. That has two consequences:

• Degaussing works: a strong magnetic field can overwrite all data on a tape. This is also true for pre-2010 HDDs, less effective for modern high-density HDDs and totally useless for SSDs.
• Shredding is straightforward: the plastic cartridge and the tape inside can be shredded into particles relatively easily.

Degaussing: strength and choice

Modern LTO tapes have a coercivity of 2000 to 3000 Oersted. That means your degausser must produce a magnetic field of at least 4000 Oersted, preferably more for a healthy margin. Consumer degaussers from the VHS era are insufficient. Use a degausser that meets NSA/CSS EPL (Evaluated Products List) or a comparable specification for your tape generation.

Warning: a wrongly set or weak degausser leaves data partially behind. The tape looks empty but forensic investigation finds fragments. Use only certified equipment or opt for physical destruction.

A tape that looks degaussed but has not been measured has no status. Only a measurement with a Magnetic Flux Meter gives certainty that the cartridge is below the detection threshold.

Shredding: the DIN 66399 T-series

DIN 66399 classifies magnetic media in the T-series:

• T-2: particles up to 2000 mm². Too coarse for personal data.
• T-3: particles up to 320 mm². Class 1.
• T-4: particles up to 160 mm². Minimum for regular personal data.
• T-5: particles up to 30 mm². For special categories and financial.
• T-6: particles up to 10 mm². Highly sensitive.
• T-7: particles up to 2.5 mm². Government and top secret.

For regular SME archives, T-4 suffices. Financial and healthcare: T-5. A good mobile shredder can handle LTO cartridges directly, without first having to take the tape out of the housing.

Degauss or shred: which to choose?

It depends on three factors.

Reuse of the cartridge

Degaussed tapes are in theory reusable (after formatting). Shredded ones are not. If you have large volumes of LTO and the cartridges are still physically usable, degaussing can be cost-attractive. But the reality is: the second-hand tape market is limited and often not worth the effort.

Provability

Shredding produces immediately visible evidence of destruction. Degaussing requires measurements and certification, which carries more administrative overhead. For audits, shredding is therefore often simpler.

Age of the tape

Old DLT and DAT tapes often cannot be degaussed reliably because the coercivity is insufficiently known. Shredding is then safer.

Preparing for destruction

1. Inventory: make a list of counts per tape type with serial or cartridge numbers.
2. Check retention periods. Sometimes a tape contains data that must still be retained legally, for example medical backups under the WGBO. Read our article on WGBO 20 years patient files if you are a healthcare provider.
3. Document the chain: who takes the tapes out of the vault, who transports, who carries out the destruction.
4. Request a certificate sample in advance, so you know which fields are captured.
5. Schedule destruction for a moment when a responsible person (DPO, IT head) can watch.

The legal side: when can the tape really go?

Backup tapes often contain a mix of data: financial administration, personal data, email archive and operational files. The retention period is the longest period that applies to any component. In practice that means:

• A tape with only payroll administration can go 5 years after end of employment.
• A tape with tax material stays retained for 7 years (AWR art. 52).
• A tape with medical data stays retained for 20 years (WGBO art. 7:454 BW).
• A tape with mixed content: look to the longest period that applies to it.

If tapes can no longer be read on a working drive, you still have to keep a retention policy for them under the GDPR. Read the tape in advance or qualify it as "illegible and therefore equated with destroyed" in the records of processing. Document that choice with reasoning.

The environmental angle

An LTO cartridge contains plastic, metal and magnetic material. After shredding, the material goes via a WEEELABEX route to a separation processor. Ask for proof of this if you produce ESG reporting. No proof? Then your chain does not close and you run into trouble in an ISO 14001 audit.

The practical approach

For a cupboard with 100 to 500 tapes, plan a one-off session with a mobile shredder. Duration: 1 to 3 hours on site. Result: an empty cupboard, a certificate, billed per kilo or per cartridge. Share the certificate with your DPO and keep a copy in your GDPR file (at least 5 years).

For large stocks (more than 1000 cartridges), an arrangement for repeat visits is common, often combined with destruction of other media.

---

Archive closure on the planning? Call us or request a quote via desnipperaar.nl. Mobile shredder at your building, certificate per job.