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Hard Drives And Their Capacity.

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Posted (edited)

Iv'e been trying to find the answer to this question for quite some time.

 

Searching on 'Google' just comes up with a whole mass of irrelevant stuff.

 

My question is this.  Is there a 'Physical' difference between say a 500GB Hard drive to a 1TB Hard drive? ( The same question is for all kinds of data storage like Memory cards, Micro SD, SD, etc etc.)

 

They look exactly the same and they weight exactly the same.!

 

So what's is it that makes them different?

 

 Is it all down to 'What you tell the Drive it is, it is'... in the software?

 

 

 

 

 

 

 

 

 

 

Edited by FinBak

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The difference is how the data is 'packed' onto the disc however it is not a case of compressing the data. 

 

In the 'old' days, data was stored on a disc in concentric rings. Each ring held the same volume of data for example 1024 characters (don't take this as gospel, it is a long time ago and my memory is going). The number of 'rings' was dependent upon the drive mechanics. One drive may have catered for 10 'rings', a different drive may have catered for 20 'rings'.  Although the physical size of the discs were the same the actual amount of data able to be held on the disc was dependent on the dive mechanics used. The 20 'rings' are closer together than the 10 'rings', so the mechanics for the 20 'ring' drive have to be finer.  Once a disc was initialised by a particular drive type (10 or 20 'rings') it could only be used on a drive with the similar mechanics unless it was initialised again (when the information is lost).

 

With the new drives and memory cards, they contain the drive mechanics and disc (or equivalent in the case of SD type cards etc) within the unit but the concept is the same but the amount of data per 'ring' is now much greater. The mechanics for the 500GB Hard drive has half the number of 'rings' compared to a 1TB Hard drive, it is all about how close together the 'rings' are. 

 

I have written this as if there is only one 'disc' (or platter) but apart from floppy discs there are in fact a number of discs (platters) mounted one on top of the other.

 

Think of a disc like a vinyl LP record but where the LP record has the data (music) recorded as one continuous grove that starts on the outer edge and spirals into the centre, the computer disc consists of numerous concentric 'rings'.  The drive mechanism controls moving the read/write (and erase) heads from one ring to another.

 

Hope this hasn't added to the confusion

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As above, it's mostly about density...

As components can shrink, the heads that read the data from the disks can also shrink, meaning finer and more tracks of data on each disk the same physical size, meaning more data per disk (or platter as they are called in a Mechanical drive) - then they can stack platters to 2, 3 or even some times 4 height within the same physical dimensions...

as for SD cards, and other flash memory, it's a similar story, but as they don't use heads, it's the number of transistors and elements within the chip that increase in numbers, as manufacturing processes improve etc, - can store more per chip, then like the platters in mechanical drives, they add more chips to increase capacity past that point.

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Posted (edited)

Thanks guys. Great replies.  Very informative and interesting stuff.

 

10 years or so ago you could get a 512MB Micro SD Card. Today you can get a whopping 512GB Micro SD Card.!

 

(Edited to add. Just found out there is a 1TB Micro SD Card)..!!

 

Amazing.!

 

Thanks again.

 

 

Edited by FinBak

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On 28/07/2019 at 14:13, FinBak said:

 

 Is it all down to 'What you tell the Drive it is, it is'... in the software?

 

 

As a side note it is possible on some removable storage to 'tell the drive' it's something else, for example take a 4GB memory stick and tell it that it's a 64GB.

 

It won't be and can't hold more than it's original size, but windows will report it as a 64GB card.  It used to be a common scam on eBay to sell small cheap memory sticks as more expensive larger ones.

 

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2 hours ago, geared said:

 

As a side note it is possible on some removable storage to 'tell the drive' it's something else, for example take a 4GB memory stick and tell it that it's a 64GB.

 

It won't be and can't hold more than it's original size, but windows will report it as a 64GB card.  It used to be a common scam on eBay to sell small cheap memory sticks as more expensive larger ones.

 

Ahh...thanks for that.  

 

 

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