Tandberg Data is modestly claiming to have the fastest 2U tape library on the market after upgrading its StorageLibrary range with the latest half-height LTO-4 drives.

Tandberg says the upgraded StorageLibrary range now provides up to 123TB of compressed storage - although the 2U model has 12 tape slots for a compressed total of perhaps 20TB.

The Norwegian storage developer has also updated its eight-slot StorageLoader - as the name implies, it's an autoloader rather than a library - with half-height (HH) LTO-4.

These compact tape drives have only been available for a few weeks, and provide an impressively high capacity - 800GB of uncompressed data per cartridge. They allow Tandberg to fit two drives into a 2U library, so the library is around double the speed of one with a single drive, at up to 1.7TB/hour. Larger libraries with more drives are even faster, of course.

Compared with LTO-3, the LTO-4 HH has double the storage capacity, runs 50 percent faster and includes 256-bit AES encryption in hardware, said Bharat Kumar, Tandberg's marketing and development VP. It supports non-erasable WORM (write-once, read-many) tapes for long term archiving, he added.

Meanwhile, rival tape library developer Overland Storage has poured cold water on Tandberg's speed claims.

"Performance is a bit of an odd thing to talk about, because the LTO-4 won't be the limiting factor - the bottleneck will be elsewhere in the system," said Chris James, Overland's European marketing director. He argued that the only real way to improve performance is to put a disk-based VTL (virtual tape library) in front of the tape library.

Not so, countered Simon Anderson, Tandberg's tape product manager. He pointed to LTO-4's ability to adjust its streaming speed so it can work efficiently even when its host server can't feed it at its rated 120MB/s.

Half-height drives are the future, he said. "If you look at the LTO roadmap, there is no full-height LTO-5 - it will be half-height only, planned for 2010."

Chris James agreed though the introduction of LTO-4 HH is significant - not least because it allows a library to host twice as many LTO-4 drives, as well as twice as much stored data.

"20TB in 2U is pretty chunky," he said. "Given that a tape library generates two percent of the heat and consumes five percent of the power of the equivalent in disk storage, there's significant space and cost advantages to had from migrating data to tape as soon as possible."

Tandberg said that a 24-slot StorageLibrary with a single IBM LTO-4 HH drive and a SCSI interface (Fibre Channel and SAS versions are also available) would sell for under $6,300 (£3,200). The smaller StorageLoader, with one LTO-4 HH and two magazines, each holding four tape cartridges, will sell for around $4,500, the company added.