Seagate confirmed on Monday that it does plan to ship a 3TB, 3.5-in Constellation ES hard disk drive this year, but cautioned that it will only be useable with PC and server makers who have upgraded their products to handle drives with capacities of more than 2.1TB.

The 3TB drive is the next generation of Seagate's Barracuda XT , which currently comes in capacities of up to 2TB and has a 6Gbit/sec. throughput and serial-attached SCSI (SAS) interface.

The 2.1TB ceiling was set about 30 years ago when a decision was made to limit the logical block address (LBA) range on a hard drive. The LBA specifies where blocks of data are stored on a hard drive.

Seagate senior product manager Barbara Craig says that a 2.5-in version is in the works. But Seagate declined to say when that drive, suitable for a laptop, would be shipping.

A 2.5-in drive could also be used in data centers to further reduce floor space requirements. Before that happens, equipment manufactures much make adjustments in order to read new 32 byte LBAs, Craig wrote in a blog post last week .

Rumours of Seagate's 3TB drive originally surfaced several weeks ago in a blog on U.K.-based tech pub, The Register . Craig then spoke with Thinq.com earlier today, confirming that the drive was coming down the pipe.

The decision was made by the industry in the early 1980s the to limit the LBA range to 16 bytes per drive sector because "they never thought we'd go beyond a 2.1TB drive," Craig said.

Software and hardware manufacturers now need to adjust everything from the operating system to the basic input/output system (BIOS) to be able to read larger 32-byte LBAs, Craig said.

Without the larger LBA, current operating systems, such as Windows XP, would only be able to access as little as one-third of the space of the new 3TB drive.

"It's a big deal," Craig said. "Everybody has to be able to access these longer addresses with their products."

There has already been a lot of work done to date to address the LBA limitation, including the creation of a Universal Extensible Firmware Interface (UEFI), which defines how software interfaces with an operating system and the hardware on which it is running on.

Updates to standard hard disk drivers are currently being tested by Seagate and Intel , according to the hard drive maker.