Linear Tape-Open - AbsoluteAstronomy.com

Linear Tape-Open is a magnetic tape data storage

Magnetic tape data storage

Magnetic tape data storage uses digital recording on to magnetic tape to store digital information. Modern magnetic tape is most commonly packaged in cartridges and cassettes. The device that performs actual writing or reading of data is a tape drive...

technology originally developed in the late 1990s as an open standard

Open standard

An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed . There is no single definition and interpretations vary with usage....

s alternative to the proprietary magnetic tape formats that were available at the time. Hewlett-Packard

Hewlett-Packard

Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

, IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

and Seagate

Seagate Technology

Seagate Technology is one of the world's largest manufacturers of hard disk drives. Incorporated in 1978 as Shugart Technology, Seagate is currently incorporated in Dublin, Ireland and has its principal executive offices in Scotts Valley, California, United States.-1970s:On November 1, 1979...

initiated the LTO Consortium, which directs development and manages licensing and certification of media and mechanism manufacturers. Seagate's tape division was spun-off as Certance

Certance

Certance was a computer tape drive manufacturer based in Costa Mesa, California. Certance made DDS tape drives and was one of the three original technology partners that created the Linear Tape-Open technology. In 2005 Certance was acquired by Quantum Corp....

and is now part of Quantum Corp.

Quantum Corp.

Quantum Corporation is a manufacturer of tape drive, tape automation, data deduplication storage products and scalable file storage software, based in San Jose, California...

The standard form-factor of LTO technology goes by the name Ultrium, the original version of which was released in 2000 and could hold 100 GB of data in a cartridge. A version released in 2010 can hold 1.5 TB in a cartridge of the same size.

Upon introduction, LTO Ultrium rapidly defined the "super tape" market segment and has consistently been the best-selling "super tape" format. LTO is widely used with small and large computer systems, especially for backup

Backup

In information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....

Historical context

Half-inch (-inch) magnetic tape has been used for data storage for more than 50 years. In the mid 1980s, IBM

IBM

and DEC

Digital Equipment Corporation

Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

put this kind of tape into a single reel, enclosed cartridge. IBM called their cartridge 3480

IBM 3480 Family

The 3480 tape format is a magnetic tape data storage format developed by IBM. The tape is one half inch wide and is packaged in a 4"x5"x1" cartridge. The cartridge contains a single reel; the takeup reel is inside the tape drive....

and DEC originally called theirs CompacTape, but later it was renamed DLT

Digital Linear Tape

Digital Linear Tape is a magnetic tape data storage technology developed by Digital Equipment Corporation from 1984 onwards. In 1994 the technology was purchased by Quantum Corporation, who currently manufactures drives and licenses the technology and trademark. A variant with higher capacity...

and sold to Quantum Corp.

Quantum Corp.

Quantum Corporation is a manufacturer of tape drive, tape automation, data deduplication storage products and scalable file storage software, based in San Jose, California...

In the late 1990s, Quantum's DLT and Sony's Advanced Intelligent Tape

Advanced Intelligent Tape

Advanced Intelligent Tape is a discontinued high-speed, high-capacity magnetic tape data storage format developed and controlled by Sony. It competed mainly against the DLT, LTO, DAT/DDS, and VXA formats. AIT uses a cassette similar to Video8. Super AIT is a higher capacity variant using wider...

(AIT) were the leading options for high-capacity, high speed tape storage for PC servers and UNIX systems. Those technologies were and still are tightly controlled by their owners. Consequently, their availability was fairly limited and prices were relatively high.

IBM, HP and Certance (spun out by Seagate, and subsequently acquired by Quantum) sought to counter this by introducing a more open format. Much of the technology is an extension of the work done by IBM at its Tucson lab during the previous 20 years.

Around the time of the release of LTO-1, Seagate's magnetic tape division was spun off as Seagate Removable Storage Solutions, later renamed Certance

Certance

which, soon after, was acquired by Quantum.

Ultrium

LTO Ultrium was developed as a (more or less) drop-in replacement for DLT and has a similar design of -inch wide tape in a (slightly smaller) single reel cartridge. This made it easy for robotic tape library vendors to convert their DLT libraries into LTO libraries.

An Ultrium cartridge's dimensions are 102.0 x 105.4 x 21.5 (mm).
An Ultrium drive reads data from a cartridge in its own generation and at least the two prior generations.
An Ultrium drive writes data to a cartridge in its own generation and to a cartridge from the immediate prior generation in the prior generation format.

Generations

LTO-5 was the latest generation; further generations are planned as tabulated below.

	Generation
Attribute	LTO-1	LTO-2	LTO-3	LTO-4	LTO-5	LTO-6	LTO-7	LTO-8
Release Date	2000	2003	2005	2007	2010	TBA	TBA	TBA
Native Native capacity Native capacity refers to the uncompressed storage capacity of any medium that is usually spoken of in compressed sizes. For example, tape cartridges are rated in compressed capacity, which usually assumes 2:1 compression ratio over the native capacity.... Data Capacity	100 GB	200 GB	400 GB	800 GB	1.5 TB	3.2 TB	6.4 TB	12.8 TB
Max Speed (MB/s)	20	40	80	120	140	270	315	472
Compression Data compression In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use.... Capable?	Yes "2:1"					Planned "2.5:1"
WORM Write Once Read Many A Write Once Read Many or WORM drive is a data storage device where information, once written, cannot be modified. On ordinary data storage devices, the number of times data can be modified is not limited, except by the rated lifespan of the device, as modification involves physical changes that... Capable?	No		Yes			Planned
Encryption Encryption In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information... Capable?	No			Yes		Planned
Partition Capable?	No (1)				Yes (2)	Planned
Tape Thickness	8.9 μm		8 μm	6.6 μm	6.4 μm
Tape Length	609 m		680 m	820 m	846 m
Tape Tracks	384	512	704	896	1280
Write Elements	8		16
Wraps per Band	12	16	11	14	20
Linear Density (bits/mm)	4880	7398	9638	13250	15142
Encoding	RLL 1,7 Run Length Limited Run length limited or RLL coding is a line coding technique that is used to send arbitrary data over a communications channel with bandwidth limits. This is used in both telecommunication and storage systems which move a medium past a fixed head. Specifically, RLL bounds the length of stretches ...	RLL 0,13/11 Run Length Limited Run length limited or RLL coding is a line coding technique that is used to send arbitrary data over a communications channel with bandwidth limits. This is used in both telecommunication and storage systems which move a medium past a fixed head. Specifically, RLL bounds the length of stretches ... ; PRML			RLL 32/33 Run Length Limited Run length limited or RLL coding is a line coding technique that is used to send arbitrary data over a communications channel with bandwidth limits. This is used in both telecommunication and storage systems which move a medium past a fixed head. Specifically, RLL bounds the length of stretches ... ; PRML

LTO-1
- First commercially available in September 2000.
- Ultrium-1 specification is now Standard ECMA-319
- Initial capacity of 100 GB.
- Initial data transfer speed of 20 MB/s (Max.)
- Tape encoding is RLL 1,7
  Run Length Limited
  Run length limited or RLL coding is a line coding technique that is used to send arbitrary data over a communications channel with bandwidth limits. This is used in both telecommunication and storage systems which move a medium past a fixed head. Specifically, RLL bounds the length of stretches ...

LTO-2
- First mechanisms approved in February 2003. First media approved in March 2003.
- Doubled capacity to 200 GB.
- Increased data transfer speed to 40 MB/s (Max).
- Switched to PRML
  PRML
  In computer data storage, Partial Response Maximum Likelihood is a method for converting the weak analog signal from the head of a magnetic disk or tape drive into a digital signal. PRML attempts to correctly interpret even small changes in the analog signal, whereas peak detection relies on fixed...
  
  encoding

LTO-3
- First media approved in November 2004.
- Doubled capacity to 400 GB.
- Increased data transfer speed to 80 MB/s (Max).
- Introduced WORM
  Write Once Read Many
  A Write Once Read Many or WORM drive is a data storage device where information, once written, cannot be modified. On ordinary data storage devices, the number of times data can be modified is not limited, except by the rated lifespan of the device, as modification involves physical changes that...
  
  feature.
- Doubled number of write elements in head.

LTO-4
- First mechanisms approved in April 2007. First media approved in May 2007.
- Doubled capacity again to 800 GB.
- Increased data transfer rate to 120 MB/s (Max).
- Introduced drive level encryption feature using 256-bit AES-GCM
  Galois/Counter Mode
  Galois/Counter Mode is a mode of operation for symmetric key cryptographic block ciphers that has been widely adopted because of its efficiency and performance...
  
  .

LTO-5
- Specifications announced January 19, 2010. The first LTO-5 drives appeared on the market in Q2, 2010.
- Nearly doubled capacity to 1.5 TB
  Terabyte
  The terabyte is a multiple of the unit byte for digital information. The prefix tera means 1012 in the International System of Units , and therefore 1 terabyte is , or 1 trillion bytes, or 1000 gigabytes. 1 terabyte in binary prefixes is 0.9095 tebibytes, or 931.32 gibibytes...
  
  (1500 GB)
- Increased data transfer rate to 140 MB/s (Max).
- Introduced partition
  Disk partitioning
  Disk partitioning is the act of dividing a hard disk drive into multiple logical storage units referred to as partitions, to treat one physical disk drive as if it were multiple disks. Partitions are also termed "slices" for operating systems based on BSD, Solaris or GNU Hurd...
  
  feature that allows tape to be "split" into 2 separately writable areas. This feature is required by LTFS
  LTFS
  Linear Tape File System refers to both the format of data recorded on magnetic tape media and the implementation of specific software that uses this data format to provide a file system interface to data stored on magnetic tape. The Linear Tape File System format is a self-describing tape format...
  
  .

Positioning times

While specifications vary somewhat between different drives, a typical LTO-3 drive will have a maximum rewind time of about 80 seconds and an average access time (from beginning of tape) of about 50 seconds. Note that due to the serpentine writing, rewinding often takes less time than the maximum. If a tape is written to full capacity, there is no rewind time, since the last pass is a reverse pass leaving the head at the beginning of the tape.

Tape durability

15 to 30 years archival.
5000 cartridge loads/unloads
Approximately 260 full file passes. (One file pass is equal to writing enough data to fill an entire tape.)

The following durability figures are quoted from Imation corporation

Imation

Imation is a US based multi-national technology corporation that designs, manufactures and sells recordable data storage media, consumer electronics products and accessories.The company is a 1996 spin off of 3M and is headquartered in Oakdale, Minnesota...

's 2008 tape specifications:

General specifications					Lifetime Tape Durability		Approximate years of life assuming..
Tape type	Native capacity	Total tracks	Tracks written per pass	Passes to write entire tape	Total end-to-end passes	Entire-tape reads/writes	... one entire tape written per MONTH	... one entire tape written per WEEK
LTO-1	100 GB	384	8	48	9600	200	17	4
LTO-2	200 GB	512	8	64	16000	250	21	5
LTO-3	400 GB	704	16	44	16000	364	30	7
LTO-4	800 GB	896	16	56	11200	200	17	4
LTO-5	1500 GB	1280	16	80	-	-	-	-

There is a large amount of lifespan variability in actual use:

Regularly writing only 50% capacity of the tape results in half as many end-to-end tape passes for each scheduled backup, and doubles the tape lifespan.
LTO uses an automatic verify-after-write technology to immediately check the data as it is being written, but some backup systems explicitly perform a completely separate tape reading operation to verify the tape was written correctly. This separate verify operation doubles the number of end-to-end passes for each scheduled backup, and reduces the tape life by half.

Linear Tape File System

The Linear Tape File System (LTFS) is a self-describing tape format and file system, which uses an XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

schema architecture for ease of understanding & use.

It allows:

Files and directories to appear on desktop and directory listings
Drag-and-drop files to/from tape
File level access to data
Supports data exchange

With LTFS tape media can be used in a fashion like other removable media (USB flash drive

USB flash drive

A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...

, External hard disk drive, etc.).
It was first introduced with IBM LTO Gen5 drive

Tape layout

LTO Ultrium tape is laid out with 4 wide data bands sandwiched between 5 narrow servo bands. The tape head assembly straddles two adjacent servo bands, with 2 servo read heads and 8 or 16 data read/write heads. Each data head moves up and down within its own data sub-band the same width as the servo band. First, the head assembly is positioned so all tape heads are at the top of their sub-bands and 8 or 16 tracks are written in the forward direction. Then the head assembly is moved to the bottom of each sub-band and 8 or 16 tracks are written in the reverse direction. The set of tracks written at the same time is referred to as a "wrap". Alternating forward and reverse wraps are written as each data sub-band is filled up in 0,2,4,...,5,3,1 order.

When the first data band is filled (they are actually filled in 3,1,0,2 order across the tape), the head assembly is moved to the second data band and a new set of wraps is written. The total number of tracks on the tape is (4 data bands) × (11–20 wraps per band) × (8 or 16 tracks per wrap). For example, an LTO-2 tape has 16 wraps per band, and thus requires 64 passes to fill.

The block structure of the tape is logical so inter block gaps, file marks, tape marks and so forth take only a few bytes each. In LTO-1 and LTO-2, this logical structure has CRC codes and compression added to create blocks of 403884 bytes. Another chunk of 468 bytes of information (including statistics and information about the drive that wrote the data and when it was written) is then added to create a 'dataset'. Finally error correction bytes are added to bring the total size of the dataset to 491520 bytes (480 KiB) before it is written in a specific format across the eight heads. LTO-3 and LTO-4 use a similar format with 1616940 byte blocks.

WORM

New for LTO-3 was Write Once Read Many

Write Once Read Many

A Write Once Read Many or WORM drive is a data storage device where information, once written, cannot be modified. On ordinary data storage devices, the number of times data can be modified is not limited, except by the rated lifespan of the device, as modification involves physical changes that...

(WORM) capability. This is normally only useful for legal record keeping. An LTO-3 or later drive will not erase or overwrite data on a WORM cartridge, but will read it. A WORM cartridge is identical to a normal tape cartridge of the same generation with the following exceptions: the Cartridge Memory identifies it to the drive as WORM, the servo tracks are slightly different to allow verification that data has not been modified, the bottom half of the cartridge shell is gray, and it may come with tamper proof screws. WORM capable drives immediately recognize WORM cartridges and include a unique WORM ID with every dataset written to the tape. There is nothing different about the tape medium in a WORM cartridge.

Cartridges

Compliance-Verified licensed manufacturers of LTO technology media are EMTEC

EMTEC

EMTEC is part of the Dexxon Group headquartered in Gennevilliers, France and markets consumer computer data storage products and other computer related consumables. Dexxon Group's North American subsidiary, Dexxxon Digital Storage Inc. is located in Lewis Center, Ohio. EMTEC evolved from BASF...

, Imation

Imation

, Fujifilm

Fujifilm

is a multinational photography and imaging company headquartered in Tokyo, Japan.Fujifilm's principal activities are the development, production, sale and servicing of color photographic film, digital cameras, photofinishing equipment, color paper, photofinishing chemicals, medical imaging...

, Maxell

Maxell

, commonly known as Maxell, is a Japanese company which manufactures consumer electronics. The company's notable products are batteries -- the company's name is a contraction of "maximum capacity dry cell" -- and recording media, including audio cassettes and blank VHS tapes, and recordable optical...

, TDK

TDK

, formerly , is a Japanese company which manufactures electronic materials, electronic components, and recording and data-storage media, and markets them globally. Their motto is "Contribute to culture and industry through creativity"...

and Sony

Sony

, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

. All other brands of media are manufactured by these companies under contract.
Since its bankruptcy in 2003, EMTEC no longer manufactures LTO media products. Verbatim

Verbatim Corporation

Verbatim Americas, LLC is a US company that markets storage media and flash memory products. It is a subsidiary of Mitsubishi Chemical Holdings Corporation of Japan and is based in Charlotte, North Carolina.-History:...

and Quantegy

Quantegy

Quantegy Recording Solutions is a manufacturer of magnetic tape and professional external hard drives based in Opelika, Alabama. Their tape products are primarily used in analog audio and video recording studios, but they also have some use with digital data storage devices and instrumentation...

both licensed LTO technology, but never manufactured their own compliance-verified media.

Colors

The colors of LTO Ultrium cartridge shells are mostly consistent, though not formally standardized. HP is the notable exception. Sometimes similar, rather than identical, colors are used by different manufacturers (slate-blue and blue-gray; green, teal, and blue-green).

Vendor	UCC	LTO-1	LTO-2	LTO-3	LTO-4	LTO-5
Compliance-verified media manufacturers
EMTEC	Black	Black	Purple
FujiFilm	Black	Black	Purple	Slate-Blue	Green	Dk Red
Imation		Black	Purple	Blue-Gray	Teal	Dk Red
Maxell	Gray	Black	Purple	Blue-Gray	Teal	Dk Red
Sony	Black	Black	Purple	Gray	Green	Dk Red
TDK	Gray	Black	Purple	Blue-Gray	Blue-Green	Dk Red
Other brands
DELL				Blue-Gray	Teal	Dk Red
HP	Orange	Blue	Dark Red	Yellow	Green	Lt Blue
IBM	Black	Black	Purple	Slate Blue	Green
Overland					Teal
Quantum	Black	Black	Purple	Blue	Green	Dk Red
RPS		Black	Purple
StorageTek			Purple		Green
Tandberg	Grey	Black	Purple	Blue-Gray	Teal	Dk Red
Verbatim		Black	Purple	Blue-Gray

UCC means Universal Cleaning Cartridge, which works with all drives.
Different manufactures use different names for the same color sometimes. The names in the table above come from each manufacturers' own documentation.
WORM (Write Once, Read Many) cartridges are two-tone, the top half of the shell is the normal color of that generation for that manufacturer, and the bottom half of the shell is a light gray.

Cartridge Memory

Every LTO cartridge has a Cartridge Memory chip inside it. It is made up of 256 (128 on LTO1,2,3) blocks of memory, where each block is 32 Bytes for a total of 8 KB (4 KB on LTO1,2,3). This memory can be read and/or written, 1 block at a time, via a non-contacting passive RF interface. This memory is used to identify tapes, to help drives discriminate between different generations of the technology, and to store tape-use information.

Every LTO drive has a CM Reader in it. The non-contact interface has a range of 20 mm. External readers are available, both built into tape libraries and PC Based. One such reader, Veritape, connects by USB to a PC and integrates with analytical software to evaluate the quality of tapes. This device is also rebranded as the Spectra MLM Reader and the Maxell LTO Cartridge Memory Analyzer.

Leader pin

The tape inside an LTO cartridge is wound around a single reel. The end of the tape is attached to a perpendicular leader pin that is used by an LTO drive to reliably grasp the end of the tape and mount it in a take-up reel inside the drive. When a cartridge is not in a drive, the pin is held in place at the opening of the cartridge with a small spring.

A common reason for a cartridge failing to load into a drive is the misplacement of the leader pin as a result of the cartridge having been dropped. The plastic slot where the pin is normally held is deformed by the drop and the leader pin is no longer in the position that the drive expects it to be.

Older single-reel tape technologies used different means to load tape onto a take-up reel.

Labels

The LTO cartridge label uses the bar code symbology of USS-39

Code 39

__FORCETOC__Code 39 is a variable length, discrete barcode symbology....

. A description and definition is available from the Automatic Identification Manufacturers (AIM) specification Uniform Symbol Specification (USS-39) and the ANSI MH10.8M-1993 ANSI Barcode specification.

Erasing

The magnetic servo tracks on the tape are factory encoded. Using a bulk eraser (or otherwise exposing the cartridge to a strong magnetic field) will erase the servo tracks along with the data tracks, rendering the cartridge unusable.

Mechanisms

Current Compliance-Verified licensed manufacturers of LTO technology mechanisms are IBM

IBM

, Hewlett-Packard

Hewlett-Packard

, Quantum, and Tandberg Storage

Tandberg Storage

Tandberg Storage ASA was a magnetic tape data storage company based in Lysaker, Norway. The company was a subsidiary of Tandberg Data. The company was spun off from Tandberg Data in 2003 to focus exclusively on tape drives. It was purchased by the same company in 2008. Tandberg Storage developed...

Cleaning

Although keeping a tape drive clean is important, normal cleaning cartridges are abrasive and frequent use will shorten the drive's lifespan. LTO drives have an internal tape head cleaning brush that is activated when the drive senses that it requires cleaning and also when a cleaning cartridge is inserted.

Compression

The LTO specification describes a Data Compression method LTO-DC, also called Streaming Lossless Data Compression (SLDC). It is very similar to the algorithm ALDC which is a variation of LZS (a patent-encumbered algorithm controlled by Hi/Fn).

The primary difference between ALDC and SLDC is that SLDC does not apply the compression algorithm to uncompressible data (i.e. data that is already compressed or sufficiently random to defeat the compression algorithm). Every block of data written to tape has a header bit indicating whether the block is compressed or raw. For each block of data that the algorithm works on, it saves a copy of the raw data. After applying the compression function to the data, the algorithm compares the "compressed" data block to the raw data block in memory and writes the smaller of the two to tape. Every data compression

Data compression

In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

algorithm will end up increasing the size of some inputs. The extra bit used by SLDC to differentiate between raw and compressed blocks effectively places an upper bound on this data expansion.

LTO-DC achieves an approximately 2:1 compression ratio when applied to the Calgary Corpus

Calgary Corpus

The Calgary Corpus is a collection of text and binary data files, commonly used for comparing data compression algorithms. It was created by Ian Witten, Tim Bell and John Cleary from the University of Calgary in 1987 and was commonly used in the 1990s...

. This is inferior to slower algorithms such as gzip

Gzip

Gzip is any of several software applications used for file compression and decompression. The term usually refers to the GNU Project's implementation, "gzip" standing for GNU zip. It is based on the DEFLATE algorithm, which is a combination of Lempel-Ziv and Huffman coding...

, but similar to lzop

Lzop

lzop is a free software file compression tool which uses LZO and is under the GPL license.Aimed at being very fast, lzop produces files a bit larger than gzip's but with less than a tenth of the CPU use. On many benchmark sites lzop is one of the fastest compressors available...

and the high speed algorithms built into other tape drives. It should be noted that plain text, raw images, and database files (TXT, ASCII, BMP, DBF, etc.) typically compress much better than other types of data stored on computer systems. In contrast, encrypted data and pre-compressed data (PGP, ZIP, JPEG, MPEG, MP3, etc.) would normally increase in size, if data compression was applied. In some cases this data expansion could be as much as 15%. With the SLDC algorithm, this significant expansion is avoided.

Encryption

The LTO-4 specification added a feature to allow LTO-4 drives to encrypt data before it is written to tape. All LTO-4 drives must be aware of encrypted tapes, but are not required to actually support the encryption process. The algorithm used by LTO-4 is AES

Advanced Encryption Standard

Advanced Encryption Standard is a specification for the encryption of electronic data. It has been adopted by the U.S. government and is now used worldwide. It supersedes DES...

-GCM

Galois/Counter Mode

Galois/Counter Mode is a mode of operation for symmetric key cryptographic block ciphers that has been widely adopted because of its efficiency and performance...

, which is an authenticated, symmetric block cipher. The same key is used to encrypt and decrypt data, and the algorithm can detect tampering with the data.

Error detection and correction

The tape drives use a strong error correction algorithm that makes data recovery possible when lost data is within one track. Also, when data is written to the tape it is verified by reading it back using the read heads that are positioned just 'behind' the write heads. This allows the drive to write a second copy of any data that fails the verify without the help of the host system.

Prices

The price of tape drives and tapes has increased relative to hard disk drives, as disk prices dropped. the cost of an LTO-5 drive taking tapes of up to 1.5 TB true (uncompressed) capacity was about US$1800; 1.5 TB tape prices were approximately half the price of the cheapest 1.5 TB hard disks.

Sales figures

The presence of five certified media manufacturers and four certified mechanism manufacturers has produced a competitive market. This has led to attractive prices for customers and high sales volumes for manufacturers. In 2002 LTO out-shipped SDLT by nearly 2 to 1. Sales since then have dominated other "super" formats (SDLT, SAIT). As a result, Quantum discontinued development of new DLT products in February 2007 and Sony followed suit by declaring AIT End-of-Life in March 2010.

Year	Drives sold this year	Total drives sold (as of Sept.)	Total cartridges sold (as of Sept.)
2001			1,000,000
2002	175,000
2003	262,000	350,000 (July)
2004	354,000
2005	461,000	1,000,000	30,000,000
2006		1,500,000	50,000,000
2007		2,000,000	80,000,000
2008		2,500,000	100,000,000
2009		3,300,000	?

Unsuccessful LTO variants

Some planned LTO variations were not produced, or produced only briefly.

Accelis

LTO technology was originally designed to come in two form factors, Ultrium and Accelis. As of 2008 LTO Ultrium was very popular and there were no commercially available LTO Accelis drives or media. In common usage, LTO generally refers only to the Ultrium form factor.

Accelis was developed in 1997 for fast access to data by using a two-reel cartridge that loads at the midpoint of the 8 mm wide tape to minimize access time. IBM's (short-lived) 3570 Magstar MP

IBM Magstar MP 3570

The IBM 3570 is a series of tape drives and corresponding magnetic tape data storage media formats developed by IBM. The storage technology and media were introduced using the name Magstar MP, combining the IBM storage brand name Magstar with MP for MultiPurpose...

product pioneered this concept. The real-world performance never exceeded that of the Ultrium tape format, so there was never a demand for Accelis and no drives or media were commercially produced.

Multiple lengths of LTO-1 tapes

The first generation of Ultrium tapes were going to be available with 4 different cartridges, holding 10 GB, 30 GB, 50 GB, and 100 GB. Only the full length 100 GB tapes were produced.

HP LTO-1 cleaning strategy

HP LTO Gen.1 drives have a cleaning strategy that will prevent the drive from actually using the cleaning tape if it is not needed. In a change of strategy, HP LTO Gen 2,3,4 drives will always clean when a Universal Cleaning Cartridge is inserted, whether the drive requires cleaning or not.

External links

IBM's LTO Redbook – IBM System Storage Tape Library Guide for Open Systems
Linear Tape Open – Consortium Homepage
ECMA 319 – Specification of Ultrium 1
IBM LTO Ultrium Cartridge Label Specification, Revision 3
An online generator for LTO barcode labels