Tape library

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Large StorageTek Powderhorn tape library, showing tape cartridges with barcodes packed on shelves in the front and a robot arm moving in the back
Small ADIC Scalar 100 tape library, showing a robot visible on the bottom with two IBM LTO2 tape drives behind it

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.

Design[edit]

These devices can store immense amounts of data, currently ranging from 20 terabytes[1] up to 2.1 exabytes of data[2] or multiple 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[when?], 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 sequential 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.

Software support[edit]

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

Barcode labels[edit]

Tape libraries commonly have the capability of optically scanning barcode labels which are attached to each tape, allowing them to automatically maintain an inventory of which tapes are where within the library. Preprinted barcode labels are commercially available or custom labels may be generated using commercial or free software. The barcode label is frequently part of the tape label, information recorded at the beginning of the media to uniquely identify the tape.

Autoloaders[edit]

Dell PowerVault 124T Autoloader
A manual magnetic tape library, common in the 1960s and 1970s

Smaller tape libraries with only one drive are known as autoloaders.[5] The term autoloader is also sometimes used synonymously with stacker,[6] a device in which the media is loaded necessarily in a sequential manner.[7]

Other types of autoloaders may operate with optical disks, floppy disks[citation needed] and compact discs.

See also[edit]

References[edit]

  1. ^ HP StorageWorks MSL2024 Tape Library - Overview & features
  2. ^ Oracle "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)"
  5. ^ "SNIA Dictionary". Storage Network Industry Association. Retrieved 2010-01-30. "tape autoloader...[Storage System] A tape device that provides automated access to multiple tape cartridges, typically via a single tape drive." 
  6. ^ "Ten common backup/restore related questions". Sun Microsystems, Inc. Retrieved 2010-01-30. "What is a stacker (autoloader) vs a jukebox?" 
  7. ^ "SNIA Dictionary". Storage Network Industry Association. Retrieved 2010-01-30. "media stacker...[Data Recovery] A robotic media handler in which media must be moved sequentially by the robot."