Linear Tape-Open

Linear Tape-Open (LTO), also known as the LTO Ultrium format, is a magnetic tape data storage technology used for backup, data archiving, and data transfer. It was originally developed in the late 1990s as an open-standard alternative to the proprietary magnetic tape formats available at the time. Upon introduction, LTO rapidly defined the super tape market segment and has consistently been the best-selling super-tape format.

Cartridges (a.k.a. tapes) contain hundreds of meters of half-inch (12.65 mm) wide tape media wound onto a single reel. The first generation LTO cartridge was released in 2000 and stored of data. With each new generation, the capacity has increased, while maintaining the same physical size cartridge.

Mechanisms (a.k.a. drives, streamers, transports) extract the tape from the cartridge and spool it up on a second reel in the mechanism, reading or writing data as the tape moves between reels. Robotic libraries exist that can hold hundreds or thousands of LTO cartridges and dozens of mechanisms.

In contrast to other non-tape data storage formats, LTO offers high-capacity removable cartridges with a lower cost per TB and better long term stability. As an overall system, LTO requires significantly less electrical power per TB and includes built-in technologies useful for data interchange and safe-keeping, like LTFS, WORM, encryption and data compression.

Historical context

Half-inch (12.65 mm) wide magnetic tape has been used for data storage since the 1950s, starting with the open reel formats IBM 7-track and later IBM 9-track.

In the mid-1980s, smaller, enclosed, single-reel cartridge formats were developed by IBM and DEC. Although the physical tape was nominally the same width in these new formats and the preceding open-reel formats, the technologies and intended markets were significantly different and there was no compatibility between them. The IBM 3480 tape format was designed to meet the demanding requirements of its mainframe products. DEC's CompacTape was targeted at a broader market, including minicomputers and smaller systems.

Later on, it was renamed Digital Linear Tape (DLT) and eventually sold to Quantum Corporation.

In the late 1980s, Exabyte's Data8 format, derived from Sony's dual-reel cartridge 8 mm video format, saw some popularity, especially with UNIX systems. Sony followed this success with their own now-discontinued 8 mm data format, Advanced Intelligent Tape (AIT).

By the late 1990s, Quantum's DLT and Sony's AIT were the leading options for high-capacity tape storage for PC servers and UNIX systems. These technologies were tightly controlled by their owners and consequently, there was little to no competition between vendors and the prices were relatively high.

Birth of LTO

Seeing an opportunity, IBM, HP and Seagate formed the LTO Consortium, which introduced a more open format focusing on the same mid-range market segment. renamed Certance in 2003, and subsequently acquired by Quantum in 2004.

Unrealized variations

Initial plans called for two distinct LTO formats: 1) Ultrium - with half-inch tape on a single reel, optimized for high capacity, and 2) Accelis and four more are planned. Between generations, there are strict compatibility rules that describe how and which drives and cartridges can be used together.

The LTO Consortium publishes a roadmap of future generations, which states that LTO-14 will have a capacity of "up to" 913 TB.

! width=7.7% | LTO-8

! width=7.7% | LTO-9

! width=15.4% colspan="2"| LTO-10

! align="left" | Release date

| 2000

| 2003

| 2005

| 2007

| 2010

| May 2025

| Jan. 2026

! align="left" |Native capacity (uncompressed)

| 100 GB

| 200 GB

| 400 GB

| 800 GB

| 1.5 TB

| 200 GB

| 400 GB

| 800 GB

| 1.6 TB

| 3.0 TB

| 6.25 TB

| 15 TB

| 22.5 TB

| 30 TB

| 45 TB

| 75 TB

| 100 TB

! align="left" | Max speed MB/s (uncompressed)

| 20

| 40

| 80

| 120

| 140

| 160

| colspan="2" | 300

| colspan="4"

! align="left" | Encryption capable?

| colspan="3"

| colspan="9"

! align="left" | LTFS capable?

| colspan="4"

| colspan="8"

! align="left" | Max. number of partitions

| colspan="4" | 1 (no partitioning)

| 2

| colspan="7" | 4

| colspan="13" | have some level of compatibility with older generations of cartridges.

{| class="wikitable" style="border: none; background: none; font-size: smaller;"

! colspan=5 rowspan=2 style="border: none; background: none;" | Compatibility

! colspan="10" style="height:28px" | Drives

! LTO-1

! LTO-2

! LTO-3

! LTO-4

! LTO-5

! LTO-6

! LTO-7

! LTO-8

! LTO-9

! LTO-10

! rowspan=12 style="width: 28px" |

! LTO-1

! 0.1 TB

! L1

! --

| align="center"

| rowspan=2 |

| rowspan=3 |

| rowspan=4 |

| rowspan=6 |

| rowspan=8 |

| rowspan=10 |

! LTO-2

! 0.2 TB

! L2

! --

| align="center"

! LTO-3

! 0.4 TB

! L3

! LT

| colspan="2" |

| align="center"

! LTO-4

! 0.8 TB

! L4

! LU

| colspan="3" |

| align="center"

! LTO-5

! 1.5 TB

! L5

! LV

| colspan="4" |

| align="center"

! LTO-6

! 2.5 TB

! L6

! LW

| colspan="5" |

| align="center"

! LTO-7

! 6 TB

! L7

! LX

| colspan="6" |

| align="center"

! LTO-7 Type M

! 9 TB

! M8

! --

| colspan="7" |

| align="center"

! LTO-8

! 12 TB

! L8

! LY

| colspan="7" |

| align="center"

! LTO-9

! 18 TB

! L9

! LZ

| colspan="8" |

| align="center"

! rowspan=2 | LTO-10

! 30 TB

! LA

! LH

| colspan="9" |

| align="center"

! 40 TB

! PA

| colspan="9" |

| align="center"

|- style="text-align: center;"

|style="border: none; background: none;"|

| Generation

| Capacity

| Regular ID

| WORM ID

| colspan=10 |

The rules for compatibility between generations of drives and cartridges are as follows:

Drives of every generation can read and write cartridges of the same generation.
Drives from generations 2 through 9 can also read and write cartridges of the prior generation.
Drives from generations 3 through 7 can also read (but not write) cartridges of 2 generations prior.
Drives from generation 8 can reformat unused cartridges from generation 7 with a special, higher-capacity format (Type M (M8)). Once reformatted as Type M, the cartridge is only compatible with drives from generation 8.

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.

Core technology

Tape specifications

{| class="wikitable" style="text-align:center; font-size: smaller;"

! scope="row" | Generations

! width=7.7% | LTO-1

! width=7.7% | LTO-2

! width=7.7% | LTO-3

! width=7.7% | LTO-4

! width=7.7% | LTO-5

! Tape width

| colspan="12" | 12.650 mm ± 0.006 mm

! Tape thickness

| colspan=2 | 8.9 μm

| 8 μm

| 6.6 μm

| 6.4 μm

| 4.0 μm

| colspan=5| Metal particulate (MP)

| MP or BaFe

| colspan=2 | SrFe & BaFe hybrid A thin edge guard band runs along each edge. The tape head assembly, which reads from and writes to the tape, straddles a single data band and the two adjacent servo bands.

Servo bands

The servo bands contain a pattern of angled magnetic stripes permanently written to the tape at the factory. The primary use of the servo signal is to maintain the transverse position of the tape head in relation to the tape. This allows the tape head to precisely follow each track as the tape moves past at high speed. The servo signal can also encode a low bitrate data stream. This data is used to encode the longitudinal position (LPOS) of that point on the tape. In addition to LPOS, manufacturers can encode additional data in the signal.

Both drives and media should be kept free from airborne dust or other contaminants from packing and storage materials, paper dust, cardboard particles, printer toner dust etc.