Same size after deduplication

Question / Problem

After deduplicating files, the Windows "Properties" dialog still shows the same size for the containing folder. Why is this?

Answer / Solution

When deduplicating files, TreeSize replaces duplicate files by hard links, after which the physical data exists only once on the hard disk. There are however X links to this data. Each of these links is shown with the size of the physical data, this is why the Windows Explorer and by default also TreeSize shows the same size for these files and the folders they are included in.

If you take a look at the allocated space of the physical drive (e.g. in the "Drive List" in TreeSize or in the "Properties" of the drive in the Windows Explorer) you will notice the difference.

To get the correct physically allocated size of a folder, you need to look at the column "Allocated Space". In the TreeSize main application make sure that the option "Track NTFS alternate data streams and NTFS hardlinks" is turned on in the Options dialog.