Want to know about HDD size

80GB 160GB 320GB
250GB 500GB 750GB

why they have to be like this? do they have a different technology?

 

Yes and no, basically they are all different capacitites. The higher the GB, the more stuff you can store on it. What do you use your PC for?
I currently have a 640GB HDD, and with every game I own and all my stuff on it, I only just broke 50% usage.
I bought not for the capacity, but cus it has 320GB platters which give a better performance, over smaller ones.
For most people though it is just a bout capacity.
To give you an idea, with no operating system installed you could fit about 25,000 mp3s per 100GB

 

I'm not sure I really understand the question, but I will give it a shot.

Using your disk sizes as an example...Say I am disk manufacturer and I want to make an 80G, 160G, and 320G disks and I have a platter with a density that supports 80G a platter. I would put one platter in the 80G, 2 platters in the 160G and 4 platters in the 320G.

Just a simplistic explanation.

Here is a link to a good basic hard drive info site, alot of reading, but informative:http://www.storagereview.com/guide2000/ref/hdd/op/index.html

 

Current tech sizes and markitability, sure they have denser platters at a higher cost, that would be the enterprise drives and beyond. Right now in the mass market, the current sizes (320+) for hgiher density platters are the way to go. The drives are faster, hold more info per platter and are cheaper to make, and thus sell. Without maxing out the platters it makes things easier on the hardware inside the HDD and thus makes it cheaper to MFG a 320-640+GB drive at this point in time, which is also great for the consumer becuase the perfomrance benefits of the now aging perpendicular technology and higher density platters is a plus. Why they chose that size is probably dependant on not only the market but cost per GB and platter for MFG, 320GB per platter (1GB=1000MB at retail, while 1GB=1024MB in most situations) is easier to produce now, and creating odd and even HDD sizes in popular varinaces from the 60's to 640's is easy to do on their end, while making a profit. At the end of the day I'd go with the 320's or 640's, no higher or lower, no odd HDD sizes. I know that 250GB platters were popular for a long time, but as technology increases, 1TB+ per platter is totally realistic.

 

no they not based on different technology they just based on different platter size.

so 80 GB, 160GB, 320GB based on 80 GB plater, so to make it clear :

80x1=80GB
80x2=160GB
80x4=320GB

and 250, 500, 750 GB based on 250 GB plater :
250x1=250GB
250x2=500GB
250x3=750GB

so to make it simple fewer plater=higher performance

sorry for my bad english