What is tape backup?
Tape backup is the practice of writing backup data to magnetic tape cartridges using a tape drive or an automated library. Once written, cartridges can be removed and stored offline, which gives tape two enduring roles: a copy that is physically disconnected from the network and low-cost retention of data that is rarely read.
How does tape backup work?
Backup software writes data to a cartridge sequentially through a tape drive. In larger installations a library holds many cartridges and loads them into drives with a robot. Full cartridges are either left in the library for automated access or exported and moved to an offsite vault under a rotation schedule. The current standard format is LTO.
How does tape compare with disk and object storage?
Each medium suits a different part of a backup strategy.
| Property | Tape | Disk or object storage |
|---|---|---|
| Access | Sequential, after loading | Random, immediate |
| Time to start a restore | Minutes in a library, longer from a vault | Seconds |
| Offline copy | Yes, when ejected | No, but can be immutable |
| Media cost for long retention | Low | Higher |
| Operational effort | Handling, cleaning, tracking | Automated |
| Incremental-forever and instant recovery | Not suited | Suited |
Where is tape still used?
Tape remains common for long-term and compliance retention of large volumes, for archives in research and media, and wherever a rule or a risk assessment calls for a physically offline copy. Many estates use tape as the last tier behind disk or object storage: recent restore points stay online for fast recovery, and monthly or yearly sets go to tape. Tape and object storage as backup tiers describes that arrangement.
What are the practical limits of tape?
Restores from tape are slow to start and proceed one stream per drive, which makes tape a poor fit for recovering many systems at once. Media has to be stored in controlled conditions and tracked reliably. Drives read only a limited range of older generations, so long-retention sets need migration to newer media every so often. And the process depends on people handling cartridges correctly. A tape that has never been restored from is untested, so periodic restores are as important as for any other backup.
Frequently asked questions
Is tape backup obsolete?
No. Its role has narrowed to long-term retention and offline copies, where its cost and physical separation still count.
Is tape immune to ransomware?
A cartridge that is out of the drive cannot be reached over the network. Cartridges still in a library can be overwritten if the backup server is compromised.
How long does data last on tape?
Manufacturers quote decades under proper storage. In practice the limit is often the availability of drives that can read the format.