What is LTO (Linear Tape-Open) Technology.

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Linear Tape-Open (or LTO) is a magnetic tape data storage technology originally produced in the late 1990s as an open standards alternative to the proprietary tape formats that were available at the time. Seagate, Hewlett-Packard, and IBM initiated the LTO Consortium, which guides development and handles licensing and certification of consumables and backup device manufacturers.

The standard form-factor of LTO technology is called Ultrium, the original version of which was launched in 2000 and could hold 100 GB of data in a single tape. The newest version was released in 2010 and can save 1.5 TB in the same size tape cartridge. Since 2002, LTO has emerged as the best selling high end media format and is widely used with corporate systems.

LTO History
1/2″ magnetic tape has been used for data storage for more than 50 years. About 30 years ago, IBM and DEC put this kind of tape into a single reel, enclosed cartridge. IBM called their tape cartridge 3480 and DEC originally called theirs CompacTape, but later it was relaunched as DLT and sold to Quantum. In the late 1990s, Quantum’s DLT and Sony’s Advanced Intelligent Tape (AIT) were the leading options for high-capacity, high speed tape storage for PC servers and UNIX systems. Those formats arehave been tightly controlled by their proprietors. Consequently, their availability was fairly restricted and prices were relatively high.

IBM, HP and Seagate attempted 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.

LTO technology was designed to be available in two form factors, Ultrium and Accelis.  Over the last few years the Ultrium format has been very popular, and there are no commercially available LTO Accelis drives or tapes. In common usage, LTO generally refers only to the Ultrium form factor.

LTO Ultrium was developed as a more or less drop-in replacement for DLT. This made it easy for robotic tape library vendors to change their DLT libraries into LTO libraries.

An Ultrium drive is expected to read data from a media cartridge in its own generation and at least the two prior generations.

Current LTO Generations
LTO-1 100GB
LTO-2 200GB
LTO-3 400GB (800GB)
LTO-4 800GB
LTO-5 1.5TB (3TB)

The cartridges last between 15 to 30 years in archives.

LTO Tapes use an automatic verify-after-write technology to immediately verify the information as it is being written, however some backup systems explicitly perform an entirely separate tape reading process to check the media was saved correctly. This separate verify procedure doubles the number of end-to-end passes for each backup, and therefore reduces the tape life by 50%.

Write Once Read Many (WORM) capability was introduced with LTO3 cartridges. This is usually only used where there are legal requirements such as in financial institutions. An LTO-3 (and later) drives will not erase or overwrite data on a WORM tape, but will read it. A WORM media cartridge is identical to a normal media cartridge except its LTO-CM chip distinguishes it to the drive as WORM and the servo track is slightly different to allow verification that data has not been modified, and may come with tamper proof screws. WORM capable drives instantly distinguish 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 tape cartridge. Typically the WORM cartridges have a different colour packaging.

Although keeping a tape drive clean is useful, the cleaning cartridges are abrasive and regular use will shorten the drive’s lifespan. HP LTO Gen 2,3,4 using a Universal Cleaning tape cartridge will always clean when a cleaning tape cartridge is inserted, irrespective of whether the drive requires cleaning or not.

The LTO-4 spec 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-GCM. The same key is used to encrypt and decrypt data, and the algorithm can detect tampering with the data.


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