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Overview - Mainframe Class 1/2" Tape Formats

Tape systems have always been an integral part of mid to large computer systems, and are now increasingly found on PC workstations performing the two equally important roles of data Interchange and data back-up / archiving.

In line with technological advances, several 1/2" formats have become established over the years. These have been developed by IBM as de-facto standards within the computer industry, and are recognised worldwide. These formats are described below :

1/2" 9-track Reel : The oldest and probably best-known magnetic tape standard. Typically on 7" or 10" reels, this format has become the universal method of exchanging data. Standard bpi recording densities of 800, 1600 & 3200 have been used in the past with 6250bpi now the most common. The 9-Track tape drives supplied by Interchange Technology are able to read and write data at all four densities.The capacity of the tape depends on several factors such as reel size, density and block size used to record the data. The low capacity of the reels compared with more modern tape formats now limits the main use of this media to high quality data interchange. Even so, this format will remain a universal medium for years to come - It is estimated that over 90% of the worlds data mine is still held on 9-Track tape!.

IBM 3480/90/90E : Introduced as a successor to 9-Track, this format uses 1/2" tape encased in a 4"x4" cartridge. Compared to reel media the cartridge is smaller, records at a higher density, and is less likely to be damaged. Cartridge tape drives are usually compact devices and are easilly integrated in both office and computer suite environments.

The cartridge format makes mechanical handling very easy, and standalone drives can be supplied with autoloader systems which automate the processing of up to 15 cartridges for data transfer or unattended back-up. These drives form the basis of most of today's robotic tape library systems, with multiple devices providing a near-line storage capability of up to 4TB.

All these format standards use the same physical size cartridge, development of the original 3480 have brought about higher capacity and data transfer rates in the 3490 & 3490E. The three formats are backwards compatible, with the following differences :

3480 - Recording on 18-tracks giving a storage capacity of 200Mb.

3490 - Recording on 18-tracks and using hardware compression giving a total storage capacity of close to 1GB ( dependant on type of data ).

3490E - Recording on 36-tracks using double length tape and hardware compression giving a storage capacity of 2.4GB per tape.

IBM 3590/3590E : The newest IBM standard format developed in conjunction with media supplier 3M. This format uses a virtuallly identical cartridge to the above, but they are not compatible in any way. The recording density is 128-track and with high levels of compression and fast data transfer rates the cartridges are capable of holding up to 35GB each ( 10GB without compression ). Used in conjunction with an autoloader the read after write capability of the format makes a very safe back-up device where data is 'mission critical'

Originally an IBM only product, this system has mainly been limited to mainframe sites and to large corporations able to afford the ultimate in this type of technology. However, the recent devlopment of lower cost and more compact 3590 compatible devices by other manufacturers, will enable a wider use of this format for data interchange and back-up in traditional 1/2" tape applications.

Please contact the Interchange Technology help line for advice and details on all tape formats.


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