About Tape
LTO Tape Media
Linear Tape-Open (LTO Tape) is a magnetic tape data storage technology originally developed in the late 1990s as an open standards alternative to the proprietary magnetic tape formats that were available at that time. Seagate, Hewlett-Packard, and IBM initiated the LTO Consortium, which directs development and manages licensing and certification of drive and media manufacturers.
LTO Ultrium was developed as a (more or less) drop-in replacement for DLT and has a similar design of 1/2" wide tape in a slightly smaller single reel cartridge, making it simple for tape library manufacturers to convert their DLT library offerings into LTO libraries.
The first generation of LTO Tape, called LTO-1, was commercially available in September 2000, and provided a native storage capacity of 100GB per tape cartridge, and boasted a maximum data transfer speed of 20MB/s.
The next generation of LTO Tape (LTO-2) began shipping in 2003, doubling the native storage capacity to 200GB per tape, while also doubling the data transfer speed to 40MB/s.
The third generation of LTO Tape (LTO-3) began shipping in 2005, again doubling the native storage capacity to 400GB, and again doubling the data transfer speed to 80MB/s. In addition, LTO-3 was available in a write-once read-many (WORM) format which was marketed as an alternative to Optical media, for applications requiring storage of electronic records on a medium that cannot be erased or modified. An LTO-3 WORM cartridge is identical to a standard LTO-3 cartridge, except its LTO-CM chip identifies it to the drive as WORM, so the drive will not erase or overwrite data written to it.
The fourth and current generation of LTO Tape (LTO-4) began shipping in 2007, again doubling the native storage capacity to 800GB, and providing a 50% performance increase to 120MB/s. Like its previous generation counterpart, LTO-4 is also available in a WORM format for regulatory compliance. LTO-4 also added a feature to allow LTO-4 drives to encrypt data before it is written to tape. All LTO-4 drives must be aware of encrypted tapes, but are not required to actually support the encryption process.
The next generation of LTO Tape (LTO-5) is currently under development, and expected to provide a native storage capacity of 1.6GB, and a maximum data transfer rate of 180MB/s. The release date for LTO-5 drives and media has not been announced yet.
Regarding backward compatibility, an LTO drive is expected to read data from a cartridge in its own generation, and at least the two prior generations, while it is also expected to write data to a cartridge in its own generation and to a cartridge from the immediate prior generation.
AIT Tape Media
Advanced Intelligent Tape (AIT Tape) is a high-speed, high-capacity magnetic tape data storage format that was developed and controlled by Sony, and competed mainly against DLT and LTO tape formats.
Available in two form factors, standard AIT uses a dual reel cartridge, similar to Sony's 8mm videotape products and Exabyte's 8mm data tape products, while Super-AIT (SAIT) uses a 1/2", single reel cartridge, similar to DLT and LTO. Both AIT and SAIT use a helical scan method of reading and writing the tape.
One of the most compelling features of the AIT format is that many generations are both backwards and forwards compatible. This allows multiple generations of tape drives to both read and write to multiple generations of tape media.
The first generation of AIT Tape, called AIT-1, was introduced in 1996, and provided a native storage capacity of 25GB per tape cartridge, and with a maximum data transfer speed of 3MB/s. An extended-length version of AIT-1 was later introduced, which provided a capacity increase to 35GB per tape and a performance increase to 4MB/s.
The next generation of AIT Tape (AIT-2) began shipping in 1999, increasing the native storage capacity to 35GB per tape, while doubling the data transfer speed to 6MB/s. Like with AIT-1, an extended-length version of AIT-2 was later introduced, with a capacity increase to 50GB, but with no performance increase. A write-once read-many (WORM) format of AIT-2 was introduced, which was marketed as an alternative to Optical media, for applications requiring storage of electronic records on a medium that cannot be erased or modified.
The third generation of AIT Tape (AIT-3) began shipping in 2001, doubling the native storage capacity to 100GB, and doubling the data transfer speed to 12MB/s. It wasn’t until 2006 that the extended-length version of AIT-3 was released, with a 50% increase to both, capacity and performance, thus providing 150GB of native storage, and a data transfer rate of 18MB/s. AIT-3 was also available in a write-once read-many (WORM) format for satisfying regulatory compliance.
The last two generations of AIT Tape (AIT-4 and AIT-5) were introduced in 2005 and 2006, and provided native storage capacities of 200GB and 400GB, respectively, both having maximum data transfer rates of 24MB/s. Due to numerous changes within the tape format, AIT-4 and AIT-5 are not compatible with older generations of AIT media, making a migration from AIT-3 more difficult.
Sony also developed a form factor of AIT called Super AIT (SAIT), and released two versions before announcing end-of-life. Released in 2003 and 2006, SAIT-1 and SAIT-2 provided native storage capacities of 500GB and 800GB, with maximum data transfer speeds of 30MB/s and 45MB/s, respectively. It is important to note that SAIT-2 drives were only available in libraries, and not in a stand-alone drive mechanism.
Due to the end-of-life of all AIT and SAIT tape formats, the recommended replacement is LTO, described above, and available in a variety of stand-alone drive and library systems that scale to hundreds of TB of storage capacity.