Editing Linear Tape-Open (section)

=== Compatibility ===
[[file:LTO2-IBM-drive-top-front-qtr.jpg|thumb|An LTO-2 mechanism, from IBM. This [[SCSI]] drive fits in a 5.25 inch, Full-Height [[drive bay]]. ]]
[[file:LTODrive HP-448HH.jpg|thumb|HP Half-Height LTO-2 drive in an enclosure for desktop use]]

In contrast to other tape technologies, an Ultrium cartridge is rigidly defined by a particular generation of LTO technology and cannot be used in any other way (with the exception of LTO-M8, see below). While Ultrium drives are also defined by a particular generation, they are required to have some level of compatibility with older generations of cartridges. The rules for compatibility between generations of drives and cartridges are as follows:

* Up to and including LTO-7, an Ultrium drive ''can read'' data from a cartridge in its own generation and the two prior generations. Later generations reduce read compatibility to only the previous generation: LTO-8 drives can read LTO-7 and LTO-8 tape, but not LTO-6 tape;<ref name="generation-8"/><ref name="Barium Ferrite"/><ref name="ibm-compatibility"/> LTO-9 drives can read and write from LTO-8 and LTO-9 tapes, but not LTO-7 ones. {{Citation |title=LTO Generation Compatibility |date=2024-12-20 |url=https://www.lto.org/lto-generation-compatibility/ |publisher=LTO}}
* An Ultrium drive ''can write'' data to a cartridge in its own generation and to a cartridge from the one prior generation ''in the prior generation's format''.
* Some LTO-8 drives may write previously unused LTO-7 tapes with an increased, uncompressed capacity of 9&nbsp;TB (''Type M (M8)'').<ref name="M8"/> Only new, unused LTO-7 cartridges may be initialized as LTO-7 Type M. Once a cartridge is initialized as Type M it may not be changed back to a 6 TB LTO-7 cartridge. LTO-7 Type M cartridges are only initialized to Type M in an LTO-8 drive. LTO-7 drives are not capable of reading LTO-7 Type M cartridges.<ref name="auto"/>
* An Ultrium drive ''cannot make any use'' of a cartridge from a more recent generation. For example, an LTO-2 cartridge can never be used by an LTO-1 drive; and even though it can be used in an LTO-3 drive, it performs as if it were in an LTO-2 drive.

Within the compatibility rules stated above, drives and cartridges from different vendors are expected to be interchangeable. For example, a tape written on any one vendor's drive should be fully readable on any other vendor's drive that is compatible with that generation of LTO.