Difference in orginal data and backedup data

Hi All,

I use HPDP 6.21.

For few servers I see huge difference in actual data(data in server) and backedup data.

For example: my drive size is 44GB but when I check the "Internal Database" properties it shows as 91 GB.

Any suggestions on why this happens and how to over come this would be lot lot helpful.

Thanks