Hard drive showing wrong capacity? Here's why.
 

Since we get numerous threads on this subject, I thought I would post this and sticky it.. hope it helps understand why hard drives don't format to their advertised capacity.

Determining drive capacity can be confusing at times because of the different measurement standards that are often used. When dealing with Windows and Mac based systems, you will commonly see both decimal measurements and binary measurements of a drive's capacity. In either case, a drive's capacity is measured by using the total number of bytes available on the drive. As long as the drive displays the correct number of bytes (approximate), you are getting the drive's full capacity.

Decimal vs. Binary:
For simplicity and consistency, hard drive manufacturers define a megabyte as 1,000,000 bytes and a gigabyte as 1,000,000,000 bytes. This is a decimal (base 10) measurement and is the industry standard. However, certain system BIOSs, FDISK and Windows define a megabyte as 1,048,576 bytes and a gigabyte as 1,073,741,824 bytes. Mac systems also use these values. These are binary (base 2) measurements.

To Determine Decimal Capacity:
A decimal capacity is determined by dividing the total number of bytes, by the number of bytes per gigabyte (1,000,000,000 using base 10).

To Determine Binary Capacity:
A binary capacity is determined by dividing the total number of bytes, by the number of bytes per gigabyte (1,073,741,824 using base 2).
This is why different utilities will report different capacities for the same drive. The number of bytes is the same, but a different number of bytes is used to make a megabyte and a gigabyte. This is similar to the difference between 0 degrees Celsius and 32 degrees Fahrenheit. It is the same temperature, but will be reported differently depending on the scale you are using.



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Various Drive Sizes and their Binary and Decimal Capacities



Drive Size in GB Approximate Total Bytes Decimal Capacity
(bytes/1,000,000,000)
Approximate Binary Capacity (bytes/1,073,724,841)
10 GB 10,000,000,000 10 GB 9.31 GB
20 GB 20,000,000,000 20 GB 18.63 GB
30 GB 30,000,000,000 30 GB 27.94 GB
40 GB 40,000,000,000 40 GB 37.25 GB
60 GB 60,000,000,000 60 GB 55.88 GB
80 GB 80,000,000,000 80 GB 74.51 GB
100 GB 100,000,000,000 100 GB 93.13 GB
120 GB 120,000,000,000 120 GB 111.76 GB
160 GB 160,000,000,000 160 GB 149.01 GB
180 GB 180,000,000,000 180 GB 167.64 GB
200 GB 200,000,000,000 200 GB 186.26 GB
250 GB 250,000,000,000 250 GB 232.83 GB

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Please note his thread is NOT FOR INDIVIDUAL QUESTIONS - please start your own thread if this sticky does not answer your question - but is open for discussion if anyone has anything to add.

I readed a forum thread, and someone posted that that difference was beside the explanation above, because the FAT uses some HD space.

Also, another common reason why harddrives do not show up the right capacity:
FAT16 File system: Max 2GB partitions (I think this counts FDisk with no large disk support)
FAT32 (on Win9X): 2 TB (Terrabytes)
FAT32 (on Win2000 and XP): 32Gb
NTFS (Pre SP1 installer): 127GB (or there abouts.)
NTFS (SP1 or higher): 2 TB

You also have to check BIOS constraints, and maybe update to a newer versions. Many very, very old BIOS's can't go above 8GB (or even 2Gb in some cases), and some older ones have a ~32GB limit. Some boards also hit rock bottom at about 128GB.

So what of your BIOS doesn't support large harddrives? It is possible to fit a controller card, which can get around these problems. But even using a controller card, windows limits also apply.

Without using a controller card, you can install a BIOS overlay, but these can lead to other problems with harddrives, and are not generally recomended. If you are in doubt, you can always ask here.

Great Thread Hal, just thought I would share other harddrive capacity problems I have experienced.

The file allocation table is minimal.... it's all in the math why the differences exist.

First, FAT16 file systems can only see partitions that are less than 2GB, and Windows 98 has a limiting partition size of 137GB. Anything larger, and it just doesn’t exist as far as the host machine is concerned. There are really no workarounds for these two limitations. The issue with older machines is that no matter what file system is being used, the motherboard’s BIOS may not support large capacity partitions. Yes, this hardware limitation carries over to Unix/Linux platforms, not being a software issue. There are partition limits with older BIOS chips: 137GB, 32GB, 8GB, 2GB, and 504MB, depending on the age and the type of BIOS. This leaves you a few ways to get around this limiting factor. One workaround is to install a PCI IDE card (with SATA capabilities, if needed). The other is to simply use a newer machine. A riskier third option would be to see if a newer BIOS revision was released that fixes the limitation, and to perform a BIOS flash with this update. If done incorrectly, the BIOS flash can effectively render your motherboard useless. There is one exception to the partition limitation you should be aware of among modern systems: note that if you are running Windows XP without SP1 (Service Pack 1), there is a software limitation of seeing partitions larger than 137GB. Installing SP1 fixes this issue. Windows 2000 has a similar issue with the 137GB limitation, but if you have either SP3 or SP4, the problem will be resolved. Anything lower than SP3, and you’re stuck with the 137GB limit.

~From the Data Recovery article

Remember there is a limitation with anything below ATA100 too. Anything below ATA100 can only support 137GB, it is a hardware limitation. The only way of getting around it is to install a controller card or get a new motherboard.

That's not entirely correct. In linux, the boot partition must be within the bios limit. That allows linux to load the kernel. Once the kernel is loaded, linux kisses the bios, and its hard drive size limitations, goodbye. If your not booting from the drive, it's no problem at all. Linux should see the entire drive. Windows is much more bound to the bios limits than linux.

already know this
 

i already know this and on my dell i got cheated out of 15GB, doesn't seem like a lot until you check price on 20GB hard drives. also, since lots of people are viewing this thread, please help me with problem: Drives and Storage > DLA from sonic wont stop :) thanks

Please start a new thread, sids. This sticky thread is an information thread, not one for discussing individual issues. Thank you!

Hint: Get a plug and play controller card that's compatible with your Linux distro.

Re
 

Until I ran Everest software today I always thought my HD was only 13.9gb in size as reported by the pc. However Everest tells me it is 20GB. Can anyone explain that? I run xp home on a 3 year old pentium 3 compaq with 400 odd mb of ram. I use a FAT 32 system.

The rest of your drive is taken up by the Compaq restore partition. If you open Disk Management, you will be able to see it.

lol i just wanted 2 say ur a computer EXPERT hehe i know who to ask when i have a queshion

XP also supports FAT32 partitions up to 2TB afaik. You can't create anything larger than 32GB with XP, though.

Windows 95 has an absolute 32gb drive size limit, regardless of file system. 95 original and 95A are FAT16 only, 95B and C are FAT32 capable.

Windows 98 has a 137gb drive size limitation. The 2tb is the theoretical limit of FAT32, not real world. Without a patched Fdisk, 98 has issues with drives and partitions larger than 64gb, the display is all wrong and you have to use drive percentages to set up partitions, not actual sizes.

Windows 2000 needs SP4 and EnableLargeLBA to go over 137gb, FAT32 or NTFS, XP needs SP1. I believe 2000 can create a FAT32 partition larger than 32gb, I know XP cannot.

250Gb HDD with 137Gb max problem
 

I have the following drive:

Seagate 250Gb Serial-ATA 7200rpm with 8Mb Buffer

When I use Seagate's DiscWizard it only sees 137Gb, but the BIOS sees 250Gb ok.

GLC suggested "EnableLargeLBA" needs to be switched on. In the BIOS it has Large/LBA auto or disabled. This is set to "auto". I have an Asus P5P800 Motherboard, bought a week ago.

I notice the postings on the limit in Win2000 and Win98, but I have Service Pack 4 with the Win2000 OS I am using, I think. I am just reinstalling it. [DiscWizard sees 250Gb's now - so clearly SP4 wasn't installe, sorry]

I did find a IAA utility - but this isn't supported by the 865PE chipset for my MB. So I'm worried the full 250Gb may have problems.

Even Intel though don't make clear whether the P4 3GHz 530 is an 865PE. It's all very confusing.

Dazzer

Did you format/partition the drive with Windows 2000 before installing the service pack? If so, then theres your problem. Right click my computer, then click manage. Navigate to disk management, and see what it says for your hard drive. If it says unallocated or unpartitioned space (I forget what exactly it says) then you have found the problem.

I was mistaken - it's EnableBigLBA - this is a registry key, not a bios setting. Win2K SP3 is also compliant - not just SP4.

http://support.microsoft.com/default...b;en-us;305098

I'm curious. I have the problem you described above with the 127 gb limit. I bought a new Western Digital SATA 300gb drive, with the new Asus A8N SLI Delux mobo. It has the onboard SATA, so I plugged it in, formatted it, and now when I look at the size in windows, it says 127 gb instead of 300. How do I fix this? Flash the Bios? I have drivers for the SATA controller, but those don't help. I think I might need to do this "FDisk" thing, but I don't know what it entails. Could you help?

Are you running WinXP? You need SP1 or higher to go past 132GB.It depends on the motherboard you're using but if it's a newer one you shouldn't have to.Again, if you're using WinXP you don't want to use FDISK...that was strickly for Win9x (Win95, Win98 and WinME).Next time you have a question or problem it's best to start your own thread and include more information about your computer...system specs, operating system, background programs, etc...

:) Cricket

EnableBigLBA
 

Neither 2000 nor XP seem to like large drives, and XP doesn't seem to recognise large partitions either.

Does one really have to EnableBigLBA by hand in the registry? Is there not a way to do it in admin tools in 2000?

How's it done in XP?

D

How can you know if your BIOS or motherboard supports 48-bit LBA?

There is no real rule of thumb. Generally, most boards in the last 5 years support it.

Ah okay. Thank you, GLC.

In response to this though late, I just bought a 160 gig Seagate drive that is in fact 148 gig. In plain english, this tatic of decimal versus binary amounts to nothing more than advertising fraud on the part of the companies that make these products. and the funny thing is that it's perfectly legal.
Over the years I've purchased many hard drives; this practice began primarly with the introduction of windows based systems. I currently have 2 Seagate drives; the 160 & a 80 gig both which show 148.4 and 74.2 gigs of space. After a long discussion with Seagate and all the techno-babble, plain math says I was ripped off of about 18.4 gigs of hard drive capacity.
Whether you like it or not, these companies will continue this practice unless enough people complain to the Better Business Bureau and the companies themselves.
For those who have older systems and are having trouble getting them to regonize these newer large capacity drives there is very few choices out there to gain the full use of the less than advertised capacity of the drive. Here is a few of them rank by the best choices first:
1. Get a new computer with the latest operating system. We all know that even if than old 800 pentium system works just fine, its out of date, especially after you add all those new cards and large drives. Even if your running Windows XP all you'll get for your trouble is a system that's impossibly slow & plagued with constant freze ups. This is because the slower processors will acuallly cause a "Bottleneck" effect due to the overwhelming data that's being run through it, esspecially with the newer operating systems which have a ton of background services running. Just look at the processes under your task manager to see them. Most are redundant and usless but, if you try closing most of them out be prepared for your system to shut down.

2. Like the first choice; get a new operating system. I have a friend who refuses to upgrade from Win98 to XP simply because he, like his computer is still stuck in the Twilight Zone. Whether you run a Windows based pc or a Mac, you need to upgrade and update. Windows is quickly phasing out support for even their newer versions of operating software thats pre- XP. Currently for Windows users; XP only with the SP2 update will recognize your new drive larger than a 137 gigs, without the manufacture's installation software (which is useful, since most require you to preload the software or run it at start up from a CD rom drive & there are still many out there who are using older computers whose CMOS Bios chips won't regonize a CD Drive. If you are using the new drive as a "primary or master" hard drive, rather than storage, this will really suck, as the Bios itself will only give you access to about 32 - 137 gigs of the total space depending on the age of the chip. Like the first choice; if you use older equipment as the base of your system, your going to have fits trying to get newer hardware or software to work properly.

3. Ok, so your computer is just a couple of years old, in great shape, but you already have two drives and both are filled to capacity with music, videos, or whatever. Simple, Most computers since around 2000 have at least two USB ports; buy a external drive. I say this for several reasons; its cheaper than buying a internal drive + a PCI controller card and once its set up, all you have to really do is plug it into the computer's USB port, Its portable, allowing you to use your stored files on other computers, and finally, It's nothing more than an internal hard drive in a self-contained case. Their is no difference other than price, which is not much more than a regular internal drive (shop around) and it is in its own case. It is more rugged, able resisting shock better and it very easy to remove and use as a internal drive if you so desire (though why anyone would want to do this is beyond me, you void your warranty). But, as I have come to learn, unless you buy a complete system from a good company, most computer hardware accesories manufactures will not honor them anyway and they have a myriad of excuses to give as to not to. I once bought a soundcard with the plug in amplifier chip missing and all the company would say is that I had removed it. Upon then returning it to the place of purchase, and getting no results, I then brought another of the exact same thing and had the store to install it in front of me. As soon as the tech opened it, guess what the same chip was also missing from this card as well. The only thing that saved me from losing money twice was I made the purchase at a in store site and they were a reputable company. Though, I do make some purchases on line, I research deeply any company I might consider ordering from this way.

These are just a few suggestions but, about their about the only ways to avail yourself of the full use of your new large capacity hard drive. As for the down right deceit on the part of hard drive manufactures, they should be required in plain bold english to explain on the box the actual capacity of the hard drive, or use the binary system of reporting the hard drive capacity to begin with. Yet if you look at all the other hardware that contains memory or processing chips they do exactly the same thing. A 800MHz pentium will actually only be about 797 Mhz.

Every box and hard drive ad I have ever seen states they are using 1 million bytes to equal a kilobyte... they even have it on the web pages.

hi i bought 320gb harddrive it only reconized 298 gb anyone kow how i get full 320 gb? Have windowxp

That's a correct display - please review the entire thread.

being in the computer industry for over 25 years, I have gotten so tired of dealing with this issue with people. trying to describe the 1000 vs 1024 kilobyte rule. or base 10 (human numbering) vs base 2 (computer numbering).

some get all upset saying its a conspiracy or they are trying to hide something or rip everyone off. Or they compare with memory sizes which always use base 2 numbering. So they show more memory installed than is shown on the package. Nope.. you get every byte you are paying for... all you have to do is get a property screen of the drive to see it.

here is my 160 gig drive. Notice the bytes vs GB.. so in long form.. you see that you get all bytes.. short (GB) form... looks like you are not.

http://www.cranvac.net/160gig.gif

here is my 300 gig drive to show the same at a different size.

http://www.cranvac.net/300gig.gif

Hope I didnt sound to irritated. Pictures seem to work better with people than just typing out the information.

Thanks for the info, Cranvac. I've converted the inline images to links, as we keep these forums totally dial-up friendly. As a compromise, the links are now in bold :)