What is LTO tape?
LTO tape (Linear Tape-Open) is the open standard format for magnetic tape used in backup and archiving. It is developed by a consortium of manufacturers, released in numbered generations of increasing capacity, and supported by drives and libraries from several vendors.
How do LTO generations differ?
Each generation raises the capacity of a cartridge of the same physical size. Capacity is quoted in two figures: native, which is what the tape holds uncompressed, and compressed, which assumes a fixed ratio that real backup data often does not reach, especially when it has already been compressed or encrypted by the backup software.
| Generation | Native capacity per cartridge |
|---|---|
| LTO-6 | 2.5 TB |
| LTO-7 | 6 TB |
| LTO-8 | 12 TB |
| LTO-9 | 18 TB |
What does drive compatibility mean for retention?
A tape drive reads and writes its own generation and only a limited number of earlier ones, in recent generations typically one back. A cartridge written today therefore needs either a drive of a compatible generation kept in working order or a migration to newer media before those drives disappear. For data kept ten years or more, this migration is a recurring task and cost that belongs in the retention plan.
Which LTO features matter for backup?
Several features are relevant. WORM cartridges cannot be overwritten once written, which provides a form of immutability for compliance copies. Hardware encryption in the drive protects cartridges that leave the building, and it makes key management critical, since a lost key means unreadable tapes. The Linear Tape File System presents a cartridge as a file system, which is used more for archives than for backup. Barcode labels and library inventories track which cartridge holds what.
How does LTO fit alongside object storage?
LTO offers low media cost and an offline state. Object storage offers immediate random access, parallel restores and Object Lock immutability. They are often combined, with object storage holding the restore points likely to be needed and LTO holding long-term sets. The balance depends on how often old data is read and on the effort an organization is willing to spend handling media. Tape backup covers the wider trade-offs.
Frequently asked questions
What does LTO stand for?
Linear Tape-Open. Linear refers to the recording method and Open to the multi-vendor standard.
Can a new LTO drive read old cartridges?
Only within the range the drive supports, which for recent generations is usually one generation back. Compatibility should be checked for each generation.
Is the compressed capacity figure realistic?
Rarely for backup data. Backups are usually compressed or encrypted before they reach the drive, so native capacity is the safer planning figure.