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I've got a new 500 Gb hard drive. I want to dual boot Windows and Ubuntu in it, so I've booted it with Ubuntu and GParted shows me the 500 Gb.

I set up a primary partition for Win7 and logical partitions for Ubuntu and run the installer so the partitioning takes place, but I don't let the whole install finish.

However, once I ran the Win7 installer, it will show me an HD capacity of 465 Gb.

Hm, something must be wrong. I delete all partitions and it still shows me 465 Gb. I boot in Ubuntu and run GParted again, but it also shows 465.

What happened ? I understand that a label of 500 on the hard drive cover does not mean exact 500, but I did not expect 35 Gb to vanish like that.

It's not the partition, it's the whole HD that seems to be reduced. GParted once showed 500Gb, what happened that it will only show 465 now ?

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Commenting here since all the answers are pretty much the same: It's even more confusing when the HD manufacturers use things like size*1000*1024*1000 to calculate size. –  Hello71 Jul 5 '10 at 14:56
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Also, you know Gb means Gigabit, not GigaByte. –  Hello71 Jul 5 '10 at 14:57
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The current version of GParted (not sure when this started) shows sizes in GiB, not GB, to be more specific. –  Hello71 Jul 5 '10 at 14:57

3 Answers 3

up vote 2 down vote accepted

Here's the explanation of how you got 500GB (I assume you got 500GB, not Gb! B is Byte b is bit):

According to SI, G is short from giga and it means 10^9. Hard disk manufacturers among others use that interpretation. For some strange reason, computer programmers started to use standard SI prefixes to signify different values. So for example they'd count K which means kilo as 2^10 (1024) instead 10^3 (1000). That incorrect use spread quickly and suppressed correct use in file size counting field.

In the meantime new set of prefixes with base 2 were defined. They should be used when discussing sizes in computing. Unfortunately, many programs and operating systems use the incorrect meaning. So one KiB which means kibibyte which has 1024 bytes. The prefix is Ki and means kibi and has value of 2^10(1024).

Some time ago developers, mainly of free software, started using correct prefixes. GParted is one of the programs which started using correct prefixes (I can't remember in which version and if it's the default setting). It could happen for some reason that GParted at one time showed space correctly using SI prefixes and second time incorrectly using SI prefixes.

Here are wikipedia links:
http://en.wikipedia.org/wiki/SI_prefix
http://en.wikipedia.org/wiki/Binary_prefix

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Nope. The HDDs are smaller than what they advertise.. or how could one say this really easily.

Explanation: http://www.dslreports.com/faq/9716

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This is the old "what's in a million" question.

The 500 indicated on the disk is in billions, while a gigabyte is 1024x1024x1024 which equals 1,073,741,824 bytes.

If you calculate, 500 billion bytes equals 476.8 GB.

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