Ubuntu – Difference Between Filesize and Size on DIsk

file sizefilesystem

When checking the properties of my Downloads folder I saw that it said

Total Size on Files: 5.3GB
Size on Disk: 43.0GB

I have noticed this in Windows, but I've been too lazy to inquire further because the difference was only a few percentage. Is this because of the different file system that Linux uses? Is this normal?

Best Answer

  • The smallest amount of space which can be allocated on disk is called a "sector" - historically it's been 512 bytes, but newer hard disks have larger sectors of 4096 bytes (though I'm not sure if "logical sectors" are 4096 bytes too or they're still 512 bytes).

    So if you have a file just 1 byte in size, it will still occupy 512 bytes on disk.

    Most files are far larger than a few bytes, so the difference is usually just a few percent. I'm not sure if you have hundreds of millions of tiny files in your Downloads folder, but that would explain this behavior.