if some one is trying to buy new HD, check its real size... - Page 2

fnorre · April 17th, 2005, 10:48 AM

Just read the labels on the harddrives, or at least the box (if you have a retail one). It's been like this "forever", remember it first on my ooold 800MB Maxtor disk. "Maxtor defines 1 MB as 1,000,000 bytes".

It has nothing to do with "unusable space"! And you don't need a calculator, even though I guess it's kind of practical. Computers / file systems use binary, and 2^10 = 1,024 = "closest to" 1k (1,000 = 10^3). So that's why 1 KB (kilobyte) in computers is 1,024 bytes and not 1,000 bytes. And so on... 1 MB = 2^20 = 1,048,576 bytes, 1 GB = 2^30 = 1,073,741,824 bytes.

So all you need to do to know the difference between "manufacturer GB" and file system GB is divide 400 GB = 400,000,000,000 by 2^30. Or to make it a bit easier; 400 GB / (1.024^3) = 400 / 1.073741824 = ~372 GB. Just use 400 / 1.074... close enough. Note that (as in Viper's example) they hardly ever use actual 400,000,000,000 bytes, but an approximate figure close to that (but not close to the "real" 400 GB which would be 429,496,729,600 bytes).

There is in fact some sort of new standard, which kind of helps the manufacturers. Would be better if somebody actually used it, though.

1 KiB is 1,024 bytes
1 kB is 1,000 bytes

1 MiB is 1,048,576 bytes
1 MB is 1,000,000 bytes

[edit: gah, could have saved some typing by just linking to this... http://physics.nist.gov/cuu/Units/binary.html ]

snq · April 27th, 2005, 06:32 PM

There's 2 different units.. MiB, GiB etc.. And then there's MB, GB.
I don't remember which one is what, but one of them counts 1 MB as 1,000,000 bytes and the other counts it as 2^20 = 1,048,576 bytes. Same with GB.. The manufacturers count 1,000,000,000 as 1 GB while windows sees 2^30 = 1,073,741,824 as 1 GB. That's about 7% difference which adds up to quite a bit with giant harddrives images/smilies/smile.gif

Both of them are official standards tho, but one of them uses the wrong unit. I believe GiB is 2^xx so that would be windows using the wrong unit.

SiR_dude · April 28th, 2005, 12:40 AM

Viper...2^32 isn't 1024...do you need to retake your math class? images/smilies/lol.gif

ArchfileX · June 1st, 2005, 01:54 PM

There is still more to this, the size of the drive and the partition size are not the same anyhow.

FAT/NTFS and EXT2 all use a different file allocation system, and if i can do this drunk i'll try and explain a little.

unix style FS's use 3 level page tables. for example 1024 'pages' of 4kB each. So each of the first 1023 is 4kB and then the next 1 maps to one set of 1024*4Kb and the 2nd level is 1024^2*kB so in this fashion a 32bit number will address 4gb (?) of hard drive space in a 3 level page table system.

the size of the page's will mean that when the drive is portioned to files with a journeling file system, each file will have a start block and a next block, sometimes a file will not fill a complete block, so wasted space occurs.

when partions are greated, because of the block/page sizes, a similar thing happens, hence the times when you make 2 partiions and end up with 4.5mb left over.

anyhow, i hope that is at least not completely dribbled and makes some small amount of sense.

-Archfile

April 27th, 2005, 06:32 PM	#22
snq Joined: Dec 17th, 2004 Last Online: January 1st, 2009 Location: Sweden / About 50 km from the arctic circle Age: 30 Posts: 327 Car: 1966 Chevelle 454 Rep Power: 17	There's 2 different units.. MiB, GiB etc.. And then there's MB, GB. I don't remember which one is what, but one of them counts 1 MB as 1,000,000 bytes and the other counts it as 2^20 = 1,048,576 bytes. Same with GB.. The manufacturers count 1,000,000,000 as 1 GB while windows sees 2^30 = 1,073,741,824 as 1 GB. That's about 7% difference which adds up to quite a bit with giant harddrives Both of them are official standards tho, but one of them uses the wrong unit. I believe GiB is 2^xx so that would be windows using the wrong unit. __________________ Too many cars..

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April 17th, 2005, 10:48 AM	#21
fnorre Joined: Mar 25th, 2005 Last Online: May 4th, 2008 Location: Oslo, Norway Posts: 218 Rep Power: 0	Just read the labels on the harddrives, or at least the box (if you have a retail one). It's been like this "forever", remember it first on my ooold 800MB Maxtor disk. "Maxtor defines 1 MB as 1,000,000 bytes". It has nothing to do with "unusable space"! And you don't need a calculator, even though I guess it's kind of practical. Computers / file systems use binary, and 2^10 = 1,024 = "closest to" 1k (1,000 = 10^3). So that's why 1 KB (kilobyte) in computers is 1,024 bytes and not 1,000 bytes. And so on... 1 MB = 2^20 = 1,048,576 bytes, 1 GB = 2^30 = 1,073,741,824 bytes. So all you need to do to know the difference between "manufacturer GB" and file system GB is divide 400 GB = 400,000,000,000 by 2^30. Or to make it a bit easier; 400 GB / (1.024^3) = 400 / 1.073741824 = ~372 GB. Just use 400 / 1.074... close enough. Note that (as in Viper's example) they hardly ever use actual 400,000,000,000 bytes, but an approximate figure close to that (but not close to the "real" 400 GB which would be 429,496,729,600 bytes). There is in fact some sort of new standard, which kind of helps the manufacturers. Would be better if somebody actually used it, though. 1 KiB is 1,024 bytes 1 kB is 1,000 bytes 1 MiB is 1,048,576 bytes 1 MB is 1,000,000 bytes [edit: gah, could have saved some typing by just linking to this... http://physics.nist.gov/cuu/Units/binary.html ]

April 28th, 2005, 12:40 AM	#23
SiR_dude Joined: Mar 5th, 2004 Last Online: December 12th, 2008 Location: Somewhere in rural Ontario, Canada Posts: 3,640 Car: 2000 Civic SiR Rep Power: 24	Viper...2^32 isn't 1024...do you need to retake your math class?

June 1st, 2005, 01:54 PM	#24
ArchfileX Joined: Mar 23rd, 2005 Last Online: June 23rd, 2005 Posts: 6 Rep Power: 0	There is still more to this, the size of the drive and the partition size are not the same anyhow. FAT/NTFS and EXT2 all use a different file allocation system, and if i can do this drunk i'll try and explain a little. unix style FS's use 3 level page tables. for example 1024 'pages' of 4kB each. So each of the first 1023 is 4kB and then the next 1 maps to one set of 10244Kb and the 2nd level is 1024^2kB so in this fashion a 32bit number will address 4gb (?) of hard drive space in a 3 level page table system. the size of the page's will mean that when the drive is portioned to files with a journeling file system, each file will have a start block and a next block, sometimes a file will not fill a complete block, so wasted space occurs. when partions are greated, because of the block/page sizes, a similar thing happens, hence the times when you make 2 partiions and end up with 4.5mb left over. anyhow, i hope that is at least not completely dribbled and makes some small amount of sense. -Archfile

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