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Hard disk label vs. actual capacity difference seems excessive...

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May 24, 2008 5:47:25 AM

I just purchased the Western Digital WD6400AAKS drive which is listed/sold as a 640GB hard drive. I installed it, then when in the Windows setup part where you create the partition, its shows a value of 618,xxx,xxxMB. Now in the past I've seen the number showing much lower that what appears in Windows so I thought it was a little strange but then remembered that much. Then, when I start Windows, when I right click the drive to format it, the formatting window shows 596GB :??:  I know in the past that the advertised/labeled capacity is slightly higher than what you actually get, but a loss of 40+GB?? That seems a bit excessive... This is the largest drive I have had yet since installing my '80GB' which broke down to 74.5GB total in Windows (XP), and I thought that was bad. Is this normal with drives this large? With ANY drives? Is there a way to maximize capacity? This could make a difference in my future plans :( 
May 24, 2008 6:25:29 AM

That's actually right. The hard drive maufacturers don't just give you less, they just advertise a gigabyte as something different than what Windows recognizes.

At the gigabyte level, you lose 7.2%

640x.072=46

640-46=596

This is because the hard drive manufacturers say a gigabyte is 1000 megabytes, and 1 megabyte is 1000 kilobytes, rather than 1024 like windows reads it.

So at the kilobyte level, you lose 2.4%. At the megabyte level, you lose 4.8%. At the gigabyte level, you lose 7.2%. And at the terabyte level, we will be losing 9.6%. It really is bad. Eventually we will be recieving less than 90% of what is advertised.

I'd say that something should be done to fix this, but at the same time you don't really lose anything. You still have all the space you paid for, it's just a little bit less than you might have thought it was. But you are still paying for the same space, whether they advertise it as 1kilobyte equals 1000 bytes or 1 kilobyte equals 1024 bytes.

So just make sure you are informed and know what you will be getting.

a b G Storage
May 24, 2008 7:32:40 AM

Yep, after formating a 1TB drive actually turns out to be 931MB.

The file system (format of the hard drive; NTFS, Fat32) itself takes up space too.
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May 24, 2008 8:30:02 AM

Wow that sucks. Thanks for the breakdown though. They really need to do something about that and at least put somewhere in fine print in the product details/specs the info you posted (the percents). I know they explain it somewhere but I doubt to that extent. I did NOT know the exact difference. By the way... how do you come up with those numbers anyway? Is there a brief explanation or someplace I could look that up? Not doubting you, just curious is all to see why that is.
May 24, 2008 8:32:49 AM

Yeah, so it would be 931 gigabytes, but only .904 terabytes....

Whatever, it's weird.
May 24, 2008 8:41:25 AM

johnnybiggles said:
Wow that sucks. Thanks for the breakdown though. They really need to do something about that and at least put somewhere in fine print in the product details/specs the info you posted (the percents). I know they explain it somewhere but I doubt to that extent. I did NOT know the exact difference. By the way... how do you come up with those numbers anyway? Is there a brief explanation or someplace I could look that up? Not doubting you, just curious is all to see why that is.


Well, a few months ago I was trying to figure it out. And I just knew that it was 7.2%.

So I thought about it. And the difference between 1000 and 1024 is 2.4%.

And every time you move up one, you lose another 2.4%. At first I thought the math wouldn't work out right, because the 2.4% that you off would be taking off less because you already took 2.4% off for the other transistions....

But it does work out.

I don't know. I just know we will always need bigger hard drives, with everything getting bigger and more detailed. So we will keep moving up in this fashion. Eventually they will be giving us like 50% of what they advertise... this might be in a bunch of decades, but who knows.

Also, I don't think my math can be right. It can't be linear like that, because then eventually you will be getting negative amounts.... So it must be a parabolic curve or something... which pretty much means that as we keep moving up these steps, we will increasingly lose slightly less each time. But since this is the beginning of it, we lose abour 2.4% each time.

Sorry if that was confusing. I have a hard time explaining myself sometimes.
May 24, 2008 9:50:12 AM

It's actually pretty simple stuff. Computers use a binary number system! Basically everything is 2 to the power of some number:
2, 4, 8, 16, 32, 64, 128, 256, 512 1024, 2048... and so on. If you look through that list you'll notice a few common computer numbers. (e.g. 512 mb of ram, ever wondered why its 512 not 500? or why 2Gb of ram is actually 2048 megabytes?).

So basically there are 1024 bytes in a kilobyte, 1024 kilobytes in a megabyte and 1024 megabytes in a gigabyte. So 500 gigabytes is actually 500 x 1024 megabytes which equals 512000 megabytes or 512000 x 1024 kilobytes which equals 524288000 kilobytes.

Now in the normal decimal system kilo means 1000, mega means a million etc.
So what the manufacturers sell is 640 gigabytes using the "decimal" giga, not the "binary" giga:

640 x 1000 = 640 000 "megabytes"
640000 x 1000 = 640 000 000 "kilobytes"
640 000 000 x 1000 = 640 000 000 000 "bytes"

BUT the computer reads this number in binary! So 640 000 000 000 bytes divided by 1024 = 625 000 000 kilobytes, not 640 000 000!
625 000 000 divided by 1024 = 610 351.56 megabytes
610 351.5625 divided by 1024 = 596.04 gigabytes.

So there you go! To summarize, when selling they use decimal, but the computer uses binary.

May 24, 2008 10:09:24 AM

The problem is with Windows, it kind of lies...

The binary system doesn't use Kilo, Mega, Giga, ect. That Decimal. The binary system uses Kiba, Mebi, Gibi so Windows should report your formatted storage as 596 GiB, but it doesn't, it says GB, which is incorrect.

http://en.wikipedia.org/wiki/Binary_prefix
May 24, 2008 10:16:32 AM

nvalhalla said:
The problem is with Windows, it kind of lies...

The binary system doesn't use Kilo, Mega, Giga, ect. That Decimal. The binary system uses Kiba, Mebi, Gibi so Windows should report your formatted storage as 596 GiB, but it doesn't, it says GB, which is incorrect.

http://en.wikipedia.org/wiki/Binary_prefix


I guess you're right, it isn't the hard drive manufacturers at all, it's actually windows. Because there really are technically 640 billion bytes, or 640 gigabytes. So yeah... it's just that windows doesn't tell you the correct units.
May 27, 2008 5:08:18 AM

The point is, its really the consumer who doesn't understand what they are buying.
a c 342 G Storage
May 28, 2008 4:09:41 PM

Be aware that you are not losing space. The confusion happens only if you try to mix different measurement tools. Draw the analogy of measuring a board with a ruler marked off in inches, then again in centimeters. You get VERY different numbers. If you cut the board into 4 pieces and measured each with a ruler, then added them up, it would come out OK as long as you use ONLY the inch ruler, or only the cm one, but never mix them.

HDD makers define "GB" or "Gigabyte" as 1,000,000,000 bytes. Microsoft (in Windows) defines it as 1,024 x 1,024 x 1,024 bytes, or 1,073,741,824 bytes. A "Megabyte" is 1,048,576 bytes, and it takes 1,024 of them to make a Gigabyte. As long as you stick with Windows' measurement system, the file sizes and disk capacity numbers all use the same definition. The root of the problem is that two groups are using the same term, "Gigabyte", for slightly different units, unlike the "Inch" vs "Centimeter" situation where it is clearer.

Make the tranlation once at the start. 640,000,000,000 bytes, measured in Windows' units, is 596.046 "Gigabytes" with NONE of it missing. From then on, think in Windows' definitions of the terms and it's all good.
May 28, 2008 11:13:56 PM

Yeh get this a bit...

Try my situation, i have 8x500gb drive in RAID 5... so as its in RAID-5 ill lose one drive for space because of redundancy. so 7x500gb is 3.5Tb yeh?... with Windows formatting its 3.18Tb... a difference of 320Gb... makes your 44gb seems small
a c 342 G Storage
May 30, 2008 2:57:51 PM

Chookman, it's not that bad. Each of your "500 GB" drives, as measured by the Windows definitions, is actually called 465.67 GB (if you willl agree to call one GB 1024 x 1024 x 1024 bytes). That's with NO space lost, just re-labelled using a new mearuement unit. So the 7 of them would have 3.2596 TB in Windows' units, and you actually have 3.18. You've got 0.08 TB or 80 GB of "lost" overhead on the drives, not 320GB.
May 30, 2008 9:48:43 PM

I realise this Paperdoc, was just making a point to the OP
a c 342 G Storage
May 31, 2008 12:07:03 AM

chookman said:
I realise this Paperdoc, was just making a point to the OP

Yeah, I kinda figured anyone who set up that kind of storage system knows what they're doing.
June 18, 2008 11:41:42 AM

kilobyte: 1024 over 1000
Which is 2.4% more

Megabyte 1024^2 = 1048 576 over 1000 000
Which is 4.86% more (rounded up)

Gigabyte 1024^3 = 1073 741 824 over 1000 000 000
Which is 7.37% more

Terbyte 1024^4 = 1099 511 627 776
Which is 9.95% more

The point where it passes double (103.7% more in actual fact) is when you reach 1024^30 = 2.032x10^90 over 1x10^90

That last one is 1000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000

Each bunch of 3 zeros after the first one (starting for the end) means a new name, kilo to mega to giga to tera etc. and seeing as sine we've been recording binary data we've only reached the 5th bunch of zeros I'd say that we've got a long way to go before the size of drives we are told becomes ridiculously unindicative.
May 21, 2009 2:09:22 AM

Know I'm bringing this back to life. But did I get majorly screwed on my 640gig HD. I formatted mine and after using it awhile never really looked at the actual space but when I did it says complete total usage is 514 gigabytes not 596 everyone is saying it should be. Oh yeah just got this also.. maybe barely a months worth
a b G Storage
May 21, 2009 7:33:09 AM

You may have 514 of free space on the drive, but you should definitely have 596 or so total.
a c 342 G Storage
May 22, 2009 3:50:34 PM

Hishuro said:
Know I'm bringing this back to life. But did I get majorly screwed on my 640gig HD. I formatted mine and after using it awhile never really looked at the actual space but when I did it says complete total usage is 514 gigabytes not 596 everyone is saying it should be. Oh yeah just got this also.. maybe barely a months worth


Some times there's an issue with hidden files. Even on a data-only disk, the Recycle Bin uses space. So if you add up all the files sizes you get a number. Subtract that from the Total Space on the drive and you will find it predicts the Free Space to be bigger than it is. But look closely at Used Space and you'll see it is bigger than the total of file sizes, because the Used Space includes any hidden files (like the stuff being saved n the Recycle Bin). Emptying the Recycle Bin will reduce the Used Space, but there may still be a small discrepancy for other types of hidden files.
March 12, 2011 3:32:12 PM

yadge said:
I guess you're right, it isn't the hard drive manufacturers at all, it's actually windows. Because there really are technically 640 billion bytes, or 640 gigabytes. So yeah... it's just that windows doesn't tell you the correct units.


We know in circuit design binary of say AND/OR gate of 2 inputs will be 2^2=4 different possibility of results so 2^10 is 1024 and is the system what windows are using.

It is whose fault now?
March 13, 2011 3:55:01 AM

It's the fault of close-minded people that only like numbers that they can easily understand. In their minds 1024 makes no sense at all and HAS TO BE a nice round 1000, and they just felt it necessary to change a completely meaningful bit/byte system to something that doesn't even remotely make sense just for the sake of being consistent with the international unit system. And this ends up screwing you over because you think you're buying 640GiB (Gibibyte = 1024^3 bytes) when you are actually buying 640GB (Gigabyte = 1000^3 bytes). That's right, guys, weep - they swapped Gigabyte and Gibibyte just to confuse everybody and make even more money. And since everyone knows GB but not a single soul on earth knows what the hell a GiB is, they also swapped the units so they can sell 1000 bytes for the price of 1024 (which adds up real quick as you can see). There you have it.
August 12, 2011 7:55:39 PM

Windows XP gives both values ​​640,132.382.720 bytes / 596 Gb. nice article. Greetings from Romania / Bucharest
September 4, 2011 7:07:26 AM

So the operating system should use the prefix Gi (gibi) instead of G (giga)

Also the manufacturers should make HDD's with capacity measured in binary rather than decimal??
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