virtualbox.org

The question says it all.
I do not understand how a guest OS (Win 7 ) can defrag a drive if it includes a difference created by a snapshot and then updated by normal operations.
Can someone point me in the right direction?

Hosts: Win 7 64bit SP1 32GB ram.
Guests: Win 7 64bit SP1.
VB 4.3.30

Once you take a snapshot, the original drive stops getting written to. While the data can be defragged, the original disk doesn't get defragged, only the snapshot disk gets defragged. All the data the OS thinks it needs to move around in the original disk actually gets copied into the new locations in the snapshot disk, and the snapshot gets bigger. The original disk does not change.