Hard disks are one of the most important and also one of the most interesting components within the PC. They have a long and interesting history dating back to the early 1950s. Perhaps one reason that I find them so fascinating is how well engineers over the last few decades have done at improving them in every respect: reliability, capacity, speed, power usage, and more.
This excellent chart shows the evolution of IBM hard disks over the past 15 years. Several different form factors are illustrated, showing the progress that they have made over the years in terms of capacity, along with projections for the future. 250 GB hard disks in laptops in five years? Based on past history, there's a good chance that it will in fact happen! Note that the scale on the left is logarithmic, not linear, and PC hard disks have one actuator. 
Dated back to 1956, the first ever HDD, the so - called 305 RAMAC (Random Access Method of Accounting and Control) was manufactured by IBM which radically revolutionized the way of data storage. This system could store only five MB (equivalent to 2.000 pages of text with 2,500 characters per page) and was a monstrosity - weighed 1 ton with fifty disks of 24 – inch diameter. Moreover, in average, RAMAC’s price/MB was US $10,000. It is unbelievable if comparing with today HDDs’ price.
5MB Hard Disk in 1956 - Its a hard disk in 1956. The Volume and Size of 5MB memory storage in 1956. In September 1956 IBM launched the 305 RAMAC, the first computer with a hard disk drive (HDD). The HDD weighed over a ton and stored 5MB of data.
The hard disk shown in the image is an old IBM hard disk dated in 1979. Notice how big it is.
As the age advanced, the size of the HDDs decreased and storage capacity increased. HDD with 750 GB storage capacity and 3.5 inch diameter storage disk weighs only a few ounces. The price/GB is also very cheap (around 0.37 US$ /GB). 