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Tape library

 
Sci-Tech Dictionary: tape library
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(′tāp ′lī′brer·ē)

(computer science) A special area, most often a room within a computer installation, used to store magnetic tapes.

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Computer Desktop Encyclopedia: tape library
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A high-capacity data storage system for storing, retrieving, reading and writing multiple magnetic tape cartridges. Also called a "tape automation system," it contains storage racks for holding the cartridges and a robotic mechanism for moving the cartridge to the drive.

Tape libraries are available for 3480, 3490, Magstar, Magstar MP, DLT, 4mm DAT, 8mm and Travan tape cartridges. Smaller units can have several drives for simultaneous reading and writing and may hold from a handful to several hundred cartridges. Large units support dozens of drives and hold several thousand cartridges.

Accessing data in a tape library can take from 15 seconds to a minute in order to find, retrieve and load a cartridge, making it available for reading and writing.

A Massive Tape Library
StorageTek's RedWood SD-3 tape libary is one of the largest in the world and can hold up to 6,000 helical scan cartridges. Each cartridge holds 50GB, which if fully populated would store 300 terabytes of data. (Image courtesy of Storage Technology Corporation.)

Changer Mechanism
All tape and disk libraries have a robotic-like device that retracts and inserts the cartridges and moves them to the read/write heads. This photo shows the mechanism in an AIT library from Cambridge Computer Services, Inc. www.cambridgecomputer.com). The tapes are held in a rotating carousel (left) that can hold hundreds of cartridges.

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Marketing Dictionary: tape library
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Facility used to store and maintain magnetic tapes. Tapes are usually stored on racks from which they hang vertically. A serial number and identification information is placed on each tape. Many facilities use computerized systems to assign serial numbers and tape locations. Random assignment can be used to make it more difficult for an intruder to find and steal a particular tape.

Wikipedia: Tape library
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Large StorageTek Powderhorn tape library, tape cartridges with barcodes packed on shelves in the front, robot arm moving in the back. Visible height of the library is about 180 cm.
Small ADIC Scalar 100 tape library, robot visible on the bottom, two IBM LTO2 tape drives behind it. Empty room for another four drives in the center. Tape cartridges on the left column, right column empty. Visible height is about 70 cm.

In computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes (a robot). One of the earliest examples was the IBM 3850 Mass Storage System (MSS), announced in 1974.

These devices can store immense amounts of data, currently ranging from 20 terabytes[1] up to more than 50 petabytes of data,[2] or about one hundred thousand times the capacity of a typical hard drive and well in excess of capacities achievable with network attached storage. Typical entry-level solutions cost around $10,000 USD,[3] while high-end solutions can start at as much as $200,000 USD[4] and cost well in excess of $1 million for a fully expanded and configured library. For large data-storage, they are a cost-effective solution, with cost per gigabyte as low as 10 cents USD, or at least 60% less than most hard drives, and they also provide systematic access to very large quantities of data. The tradeoff for their larger capacity is their slower access time, which usually involves mechanical manipulation of tapes. Access to data in a library takes from several seconds to several minutes.

Because of their slow random access and huge capacity, tape libraries are primarily used for backups and as the final stage of digital archiving. A typical application of the latter would be an organization's extensive transaction record for legal or auditing purposes. Another example is hierarchical storage management (HSM), in which tape library is used to hold rarely used files from file systems.

Smaller tape libraries with only one drive and robot are known as autoloaders.

Software support

There are several large-scale library-management packages available commercially. Open-Source support includes AMANDA, Bacula, and the minimal mtx program.

Most libraries have the capability of scanning barcode labels, allowing them to locate the correct tape even if it is not in the expected slot. Preprinted labels are available commercially but may also be generated using software such as HP DLT 4000 Barcode Labels.

References

  1. ^ HP StorageWorks MSL2024 Tape Library - Overview & features
  2. ^ Sun StorageTek SL8500 Modular Library System
  3. ^ HP Small & Medium Business Online Store: HP StorageWorks MSL2024 Tape Libraries
  4. ^ [1]. Cites cost as "From $195,830. (US)"
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