Western Digital is on the forefront of new hard disk technology, and is pushing to change the way they are made. The change from 512-byte sectors to 4k sectors will drastically improve hard disk capacity, in what otherwise is a gridlock between being able to correct errors on a hard disk platter versus adding more space.

If you’ve ever wondered why hard disks advertise capacities of 250 Gigabytes, 500GB or 1.0TB, yet when you format the drive under your favourite operating system it shows a (sometimes drastically) lower size, it is because of the filesystem. This physical change in sector length on a hard disk will supposedly improve space allocation on a drive by 7 – 11% immediately. Error correction speed stands to improve by 50%. This is a huge improvement.

http://anandtech.com/storage/showdoc.aspx?i=3691