Why size on disk is more than actual size?

Question

What the extra memory space for?

Answer 1

Your system writes data to disk in blocks. The size of the block depends on how big the drive is and how it's partitioned/formatted - a common size these days is 4K.

A block cannot be shared between two files, so if you create two files that are 2K each, they can't be stored on one block. Each file uses a full 4K block. Even if a file is only a few bytes in size, it still uses a 4K block of space on the drive.

Also, if you have a 26K file, it uses 28K of disk space (7 of the 4K blocks) so there's some wasted space there, too.

That's why the space used on the disk is more than the actual file size.

Answer 2

While mommadillo is totally right in what she said, I'm thinking that your question might have been "why does a 300GB hard drive only show up in Windows as a 279GB drive?"

If that was what you were wondering, it's because formatting a disk takes up some space, PLUS, the hard drive manufacturers use the 1,000 MB= 1 GB way of thinking, while Windows uses the correct way, which is 1,024KB= 1MB, and 1,024MB= 1GB. That's where most of the "space" that should be there, but isn't has gone.

Answer 3

has to do with multiples.
1.2.4.8.16,32,64,128,256,512,1024
in the olds days things were represented in K or one thousand bytes of memory or hard drive space. My first hard drive was 20 K.
when looking at the numbers above, do you see any for 1000, no. but 1024 is close, right? so that is where the extra comes from. my 20K drive wasn't 20000 bytes in size but 20x1024=20480 bytes in size.
hope this helps

Answer 4

Probably the operating system software, or at least the program that actually makes the computer do what its supposed to do.