Generate Data Grid and Export Excel for Site Collection

I have a sharepoint 2010 site collection more than 50 GB. I need to loop through each site in the site collection to fetch entire details and to export into an excel sheet.

Eg. Site collection ( size )

Site 1 ( size )

Document Lib1 (count) (size)

Document Lib2 (count) (size)

List 1 (count) (size)

Like that to loop entire information. I was using SPWeb, SPSite to loop through and it takes more than 2 hrs display in the grid and to export to excel

WHICH IS THE BEST WAY TO LOOP THROUGH AND GET INFORMATION AS REQUIRED. Please help me with suggestions. (would be better with examples)

Thanks,
Karthik