Page 72 - UNI 101 Computer Science Handout.

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one-half inch wide tape in a 102mm × 105mm × 21.5mm cartridge. The technique used for storage and

retrieval is called data streaming. The cartridge tape is divided longitudinally into many tracks, currently

as many as 886. The tape mechanism writes and reads the bits longitudinally, along the length of one
group of tracks. At each end, the tape reverses, and the next group of tracks are written or read. Data is

usually stored on the tape starting with the centermost track and moving outward toward the edge of

the tape. Error correction is built into the system, and WORM archiving is also available as an option. An
alternative data cartridge format is based on the technology that was originally developed for videotape.

These are called helical scan cartridges. The data on helical scan cartridges is very tightly packed, using

a read/write head that rotates at a highspeed top ack the tape more tightly with data. This results in a

track that is made up of diagonal lines across the width of the tape. There are two different helical scan

cartridges in common use. The smaller AIT (advanced intelligent format) uses 8-mm wide tape in tape
lengths of up to 246 meters, with a current maximum uncompressed capacity of 400 GB in a cartridge

95mm×62.5×15mm. The larger SAIT (super-AIT) cartridge contains up to 640 meters of one-half inch

wide tape, with a current maximum uncompressed capacity of 800 GB.

The SAIT cartridge is the same size as the LTO cartridge, but the two types of cartridge are not
interchangeable. Figure below shows the track layouts for both types of cartridges.

Figure 11 Data Cartridge Formats.

72 Academic Year 2025/2026