I've noticed that long fsck on disks for old snapshot.debian.net is completed today. It takes 75 days! Anyway, it didn't end successfully. It seems that some filesystem erros remain. By forcing mount the filesystem, I couldn't any files but lost+found, and it did't finish to list in lost+found directories, not only filesystem still had errors but also too many files were moved into lost+found. I'm afraid it's impossible to restore old archive...