Tape library

Tapes and batch processing In the mainframe computer era, especially the IBM mainframe, the most common format in use was the 9-track tape. In addition, the set of update transactions themselves might constitute a second input tape. The master file output of one update job would then be the master file input to the next time the job is run, perhaps a day, a week, or a month later. and library sizes of several thousand reels of tapes were commonplace. These people were the ones responsible for mounting tapes onto tape drives as part of running a job. Overwriting a tape that was meant to be preserved was another potential mistake. Supporting software Tape management systems of this era were software packages whose purpose was to help facilitate tape library operations and management. They kept track of data sets on tape, and produced reports indicating whether a data set should be retained on, or could be scratched from, a tape; they aided in the setup and running of scheduled production jobs, through such things as tape pull lists and pre-printed external gummed tape labels; and they kept track of the physical inventory of tape reels. The most popular of these packages was UCC-1 from University Computing Company, a product that was also known as the Tape Management System. It made several appearances on Datapro Research Corporation's Software Honor Roll. and a third was TLMS II from Capex Corporation. As use of the mainframe continued on into the following century, tape library management, both manual and automatic, was one element of the offerings of the Data Facility Storage Management Subsystem (MVS) from IBM. == Automated era ==

Powderhorn tape library, showing tape cartridges with barcodes packed on shelves in the front and a robot arm moving in the back Scalar 100 tape library, showing a robot visible on the bottom with two IBM LTO2 tape drives behind it Design Physically automated tape library devices can store immense amounts of data, ranging from 20 terabytes up to 2.1 exabytes of data as of 2016. Such capacity is multiple thousand times that of a typical hard drive and well in excess of what is capable with network attached storage. Typical entry-level solutions cost around $10,000 USD, while high-end solutions can start at as much as $200,000 USD 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 2 cents USD. 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 There are several large-scale library-management packages available commercially. Open-source implementations include AMANDA, Bacula, and the minimal mtx program. Barcode labels 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 medium to uniquely identify the tape. Autoloaders Smaller tape libraries with only one drive are known as autoloaders. The term autoloader is also sometimes used synonymously with stacker, a device in which the media are loaded necessarily in a sequential manner. Other types of autoloaders may operate with optical discs (such as compact discs or DVDs) or floppy disks. ==See also==