Why does my 500GB hard disk only give me 465GB of space when formatted?
Now that large hard disks are amazingly cheap and getting more common every day, I've noticed many people posting questions similar to the above on various message boards. The implication seems to be that the formatting process is somehow responsible for consuming ~36GB of a 500GB disk.
The truth, however, is that ever since the first 1GB hard disk was produced, manufacturers have conveniently chosen to use a non-standard definition of exactly how many bytes there are in a gigabyte.
The computer industry has always defined a kilobyte as 1,024 bytes (2 to the power of 10) and a megabyte as 1,024 kilobytes (2^20) so it is only logical that a gigabyte would be 1,024 megabytes (2^30). In terms of number of bytes, 1GB defined this way is 1,024 x 1,024 x 1,024 = 1,073,741,824 bytes. The hard drive industry, though, defines a gigabyte as a billion bytes. That is, 1,000 x 1,000 x 1,000 = 1,000,000,000 bytes.
Since Windows Explorer (and just about every other program that displays file and drive sizes) uses the computer-industry standard definition of what a gigabyte is, it takes the capacity of the drive (500,000,000,000 bytes), divides it by how many bytes it says there are in a gigabyte (1,073,741,824) and comes up with...465GB.
As long as hard drive manufacturers continue to assert 1GB == 1 billion bytes, consumers will still get confused when they get their new hard drive installed and find that it is ~7% "smaller" than they expected.
For those that may choose to quibble with my assertion of exactly what is "standard", I realize this puts me in disagreement with the IEC, IEEE, NIST etc. But if it really were the case that 1GB = 1 billion bytes is the accepted norm, why would hard drive manufacturers opt to settle the class action lawsuits that arose over this very issue?
More information on this topic can be found on Wikipedia here.
The truth, however, is that ever since the first 1GB hard disk was produced, manufacturers have conveniently chosen to use a non-standard definition of exactly how many bytes there are in a gigabyte.
The computer industry has always defined a kilobyte as 1,024 bytes (2 to the power of 10) and a megabyte as 1,024 kilobytes (2^20) so it is only logical that a gigabyte would be 1,024 megabytes (2^30). In terms of number of bytes, 1GB defined this way is 1,024 x 1,024 x 1,024 = 1,073,741,824 bytes. The hard drive industry, though, defines a gigabyte as a billion bytes. That is, 1,000 x 1,000 x 1,000 = 1,000,000,000 bytes.
Since Windows Explorer (and just about every other program that displays file and drive sizes) uses the computer-industry standard definition of what a gigabyte is, it takes the capacity of the drive (500,000,000,000 bytes), divides it by how many bytes it says there are in a gigabyte (1,073,741,824) and comes up with...465GB.
As long as hard drive manufacturers continue to assert 1GB == 1 billion bytes, consumers will still get confused when they get their new hard drive installed and find that it is ~7% "smaller" than they expected.
For those that may choose to quibble with my assertion of exactly what is "standard", I realize this puts me in disagreement with the IEC, IEEE, NIST etc. But if it really were the case that 1GB = 1 billion bytes is the accepted norm, why would hard drive manufacturers opt to settle the class action lawsuits that arose over this very issue?
More information on this topic can be found on Wikipedia here.
posted by noegruts at
Monday, March 10, 2008
2 Comments
