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I just got a new Lenovo Laptop which has been installed with Windows 7 and is supposed to have 250G hard disk.

Windows 7 reports that the hard disk drive has two parts: 221GB "C:" and 9.76GB "Lenovo Recovery". The sum of the two parts is 230.76GB.

If I remember correctly, if divide 250G by 1024 three times, I will get 232.8GB, which should be what the OS reports as the hard drive size. But why the sum 230.76GB of the two parts of hard drive is still smaller than 232.8GB?

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5 Answers

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Because NTFS by design uses a piece of your volume for a MFT (Master File Table) which holds file names, creation dates, access permissions, and contents as metadata. The bigger the volume, the bigger the chunk NTFS will need.

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Do you also mean the whole C: disk size does not include the size for MFT? Is there some place under Windows reporting the size of the whole hard drive? – Tim Nov 18 '09 at 4:58
Yes, The size reported is not including the MFT. I don't think anything within Windows will report the full actual size of the disk including the part the MFT is taking up. – John T Nov 18 '09 at 5:19
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No, the size does include the MFT. Think about it the MFT can grow so it the size didn't include the MFT you would see the size of the drive drop. Also in Disk Management if you switch the format from NTFS to FAT the size of the partition doesn't change. – shf301 Nov 18 '09 at 6:18
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@shf you are very misinformed, and very downvote happy. First of all, the MFT size is defined by the size of your drive, and it is made once. This space allocated does not change in size, it preallocates enough up front for future changes. Also once you changed to FAT32, try a reboot? – John T Nov 18 '09 at 6:50
Maybe you are thinking of the MFT zone which NTFS reserves, but that is not the size of the MFT itself and that zone can be used to store files if the rest of the drive is filled. See technet.microsoft.com/en-us/library/cc781134%28WS.10%29.aspx – shf301 Nov 19 '09 at 5:20
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up vote 4 down vote

Actually. This is because harddrive manufacturers conform to the 1MB = 1,000 KB rule and your OS uses the 1MB = 1,024 KB rule.

This would probably account for most of your lost space. Its normal. You will NEVER buy a drive that is the size it specifies, ever. I looked in to it myself not too long ago :)

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Ah, you mentioned something like that also. Ah well, good clarification for everyone else! :D Also, NTFS holds additional space/information for each additional partition used, so you will probably never see 100% of your space within Windows. – SevenT2 Nov 18 '09 at 5:33
All the drives you buy are the size they specify. Your software is just reporting the size wrong. – endolith Jun 15 '11 at 4:59
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up vote 2 down vote

Unfortunately, life's a bitch and this is one of those things that annoys people non stop.

At least you are smart and understand that there is a conversion that needs to be made.

The "extra" space is usually used up by the allocation table, meta data and various other items that just make it work without you needing to think of it... it is nothing to worry about.

If you want to make 100% sure you have the correct drive, go in to device manager and expand hard drives, find the model number and Google it. If it reports the correct drive (which it should) there shouldn't be anything to worry about.

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up vote 2 down vote

A chunk of your loss at least is due to the partition table eating it's entire track--a horribly inefficient legacy we are left with.

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up vote 2 down vote

It could just be the manufacturer rounding the hard drive size to the nearest whole gigabyte. If we start with what Windows shows and calculate what that work out to in billion bytes:

232.8 * 2^30 / 10^9 = 249.9671 million bytes

So they just rounded the marketing size to 250, cause whose going to miss 0.0329 million bytes.

If you can get the module number of the hard drive and get it's detailed specs and find it's sector count you can determine what the actual capacity of the drive really is.

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