SQL SERVER – SQL Daily Tips – Space Unused Vs Space Unallocated

Space Unused:

Are pages allocated on extends, however this pages are not used yet by any kind of objects. It means, SQL Server has 8 pages by each extent. If an object reside in a page of a certain extend, this space is allocated and used, but the rest of the space of the extend is allocated but unused because there are not objects.

Space Unallocated:

Space (extends) that is not in use, it means extends that are not allocated by SQL Server. Any kind of grow will produce a space unallocated.