Ever since the first 1TB 3.5" hard disks hit the market early 2007, there has been little news about any higher capacity models, apart from external drives that use multiple hard disks to provide their advertised capacity.  Going by this Tech Radar report, Hitachi is aiming to make a major leap in capacity by working on a 5TB 3.5" hard disk, which it expects to have ready by 2010.  The drive will use improved perpendicular recording technology, which can achieve over 1TB per square inch. 

The one problem hard drive manufacturers now face is the growing threat from solid state disks, particularly with flash memory pricing gradually dropping bit by bit.  If Hitachi can manufacture the 5TB drive for a reasonable price, it should still give it the competitive advantage over SSDs should the flash memory prices make a massive plunge over the next couple of years.

According to the source, Yoshihiro Shiroishi from Hitachi reckons that it will take just two of these 5TB hard disks to provide the same storage capacity of an average human brain.