Hard Disk Space Usage - Missing GB?

Question

This question might seem strange, but please bear with me.

I have a 1TB external hard disk from Seagate. I know that 1TB is 1024GB, but when I connect it to my PC it shows me only 931GB.

1) Where is the remaining 93GB?

I have four folders in my above said HDD.When I select the four folders and check the properties, it shows me 129GB total, but when I check the properties of my HDD by right clicking it, it shows me 137GB as used.

2) Where is the rest 8GB?

Please note that there are no hidden files or folders, no bad sectors etc..

The HDD is formatted in FAT32 file system.

Where does all these space go?

Answer 1

1:

You're wrong, actually, when you state that 1 TB is 1024 GB.



Hard disk vendors use SI prefixes. That means that 1 TB is NOT 1024 GB, it is 1 * 10^12 bytes, or 1000 * 1000 * 1000 * 1000 (1000^4) bytes.



Your operating system uses binary prefixes. 1 TiBi is (1024^4) bytes.



See the difference? That's where your 93 GB goes.



The difference in definitions on the Terabyte level is about 9%.



2:

Well, this is slightly more tricky. In FAT32, you assign "sectors" to a file. That means that there's a minimum size for any file on your computer. That can be specified if you go to the properties of the drive itself, and look around there.



So, for instance, consider that you have a FAT32 disk that has a minimum size of 4kB. If the file is only one character, it will still use 4 kB. If it goes over 4 kB, it gets another sector, and the cycle repeats. So in this case, quite a lot of space will be "wasted" because of the granularity of the sectors assigned to the file.



That's why your hard drive shows you 129 GB total (which is the size of the files) and 137 GB used (which is the space taken up in the file system).



Incidentally, this is one of the reasons why it is smart to format large drives as NTFS or something similar - the FAT32 file system just doesn't handle large drives very well.

Answer 2

It turns out that the answer has to do with your electronic devices and their operating systems using a different definition of "gigabyte" ("GB") than that of the manufacturer's of storage devices such as memory cards and hard drives. When manufacturers of such devices say "GB", they mean what is called a "decimal gigabyte", which equals exactly 1,000,000,000 (one billion) bytes (a byte is a fairly basic unit of storage in computers). When your device's operating system describes the capacity of the storage medium, they typically use what is called a "binary gigabyte", which equals exactly 1,073,741,824 bytes. Because of this discrepancy, a device has less binary gigabytes than decimal gigabytes.



It turns out that a decimal gigabyte is approximately 93% the size of a binary gigabyte, so if your hard drive is 40 decimal gigabytes, your operating system will report that it is approximately:



40 decimal gigabytes * 93% = 40 * 0.93 = 37.2 binary gigabytes



Which is exactly the hard disk capacity that is reported by operating systems such as Windows XP. Likewise, a 1 decimal terabyte hard drive is 1000 decimal gigabytes. Windows will report that hard disk's capacity as approximately:



1000 decimal gigabytes * 93% = 1000 * 0.93 = 930 binary gigabytes (this is very close to what Windows reports; however, the multiplication factor isn't exactly 0.93, as we'll see below)



So simply put, when you purchase a digital storage medium, you can expect your operating system to identify it as being about 93% the size that you expect it to be. You're not being ripped off; it's just that the word "gigabyte" is used to mean two different things.

Answer 3

It uses that space for configuration and a file table. ie, what space is left, what files are on it, their size and location.

Answer 4

I believe this space on the HDD is dedicated to your startup software.