Wednesday, December 17, 2008

What's The Difference Between Size And Size On Disk In Folder Properties

Many people don’t understand the difference between these two values:



Today I run into small blog post that describe these two values. However there is something I am still missing in Windows. We should be able to see 3 values:


Size on disk

Virtual size on disk

Why is that? Because especially with Windows Vista\2008\7, softlinks and hardlinks are playing much more important role.

For example take folder WinSxS in Windows directory. If you check it’s size, you will be probably surprised that it is really big, in my case it is 10GB. Surprisingly this folder is NOT that big, because most files (or many of them) are in fact only hardlinks to existing files.

Confusing? Yes

Do you know real size of that folder? No

Same applies to my “loopback” symlink. I tried to use utility (Gladinet) that allows you to share some folders between computers. However I didn’t wanted to share only folder, I wanted to share whole C: drive (which is as far as I know not supported by that utility). So I used simple trick and created C:\Links\Loopbacks\C folder that is symlink to C:\. Worked great :) But as you can see below, that folder is really big (even though it DOESN’T occupy 75GB on my disk):


I think this can be pretty confusing\annoying in some situations – in my case if I would calculate size per folder, it would be at least 150GB (on my 110GB HDD) :)

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