Sony has launched AIT-4, the fourth generation of its Advanced Intelligent Tape format. There is 200GB of native capacity, double that of the preceding AIT-3. The doubling is achieved by an areal density increase from 720 Mbit per square inch to 1170Mbit per square inch, a seven percent longer tape and an optimised data structure. These figures fit in with the forecasted values used in our AIT & VXA comparison.

Compressed capacity, at 2.6:1 compression is 520GB, and compressed I/O rate is 62.4Mbit/s. AIT-4 sustained transfer rate is 24Mbit/s, again double that of AIT-3's 12Mbit/s. There is a higher head drum rotation speed, advanced read heads and AME (advanced metal evaporation) tapes, which all increase the I/O rate. Mark Lufkin, a general manager in Sony Europe's storage solutions division, said: "AIT-4 offers a backwards compatible upgrade path to our existing AIT-1, 2 and 3 products. There were 500,000 AIT drives and 10 million AIT media in use during 2003." Lukin said. AIT is replacing DDS as the entry-level tape format; "According to IDC, AIT has become the number one DDS replacement format and our market share has nearly doubled in one year."

AIT was developed in the mid-90s, by Sony, when it wanted to offer siginficantly more capacity than the then current DDS 4. The other DDS consortium members, HP and Seagate, now Certance, have developed DAT-72 which offers 36GB, equivalent to AIT1's 35GB. DDS has been left a long way behind.

AIT4 is not an entry-level in itself though, being mid-range; it is compatible with AIT1 and 2 which are entry-level formats.

Other mid-range 200GB capacity level tapes use half inch media and linear recording technology, contrasting with Sony's 8mm helical scan recording. They include Quantum's SDLT600 at 300GB native. The earlier SDLT320 offers 160GB. The LTO consortium of HP, IBM and Seagate has LTO 2 at 200GB with LTO 3 expected next year at 400GB. A transfer speed of 20Mbit/s for LTO 2 means Sony's new format is 20 percent faster. SDLT600 is much faster at 32Mbit/s.

Quantum's VS80 entry-level format is 40GB native with its VS160 offering 80GB. These roughly match AIT1 and 2. Sony says AIT spans the entry level to mid-range superdrive-class requirements with a single scalable format. It claims that no other format does. Quantum says its Value DLT and SDLT formats do constitute an entry-level to superdrive offering. For example, SDLT 320 is backward-read compatible with VS80 using DLTtapeIV media. SDLT 600 is backward-read compatible with VS160 drives.

The AIT roadmap has AIT5 and 6 generations offering 400GB and 500GB respectively. Sony also has its Super AIT format with SAIT1 currently offering 500GB native capacity in its half-inch helical scan format. AIT-4 drives will ship for evaluation in the second quarter of this year with volume shipments in the autumn. Sony autoloaders and libraries will be updated to use the format. No pricing information has been issued.