Overview - Mainframe Class 1/2" Tape Formats
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 :
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.
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.
Recording on 18-tracks and using hardware compression giving
a total storage capacity of close to 1GB ( dependant on type
of data ).
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'
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"
contact the Interchange Technology help line for advice and
details on all ½” tape formats.