Freshly formatted ext4 drive appears to have several gigabytes already used

I have setup several drives in an Ubuntu 12.04 x64 machine by deleting all the partitions and formatting them as ext4 with fdisk, but when I ran df -h, it showed me that a substantial amount of the drive space had already been used up. For example, on my 1TB drive, it showed me that 14GB was already in use. I mounted the drive to a folder and went to examine it with ls -a and there are no files except for a directory lost+found that contains no files which really confuses me. Where are these 14GB "hiding"? I have tried re-partitioning it twice and un-mounting and then mounting again but no luck. Must I run dd to wipe the drive with /dev/null to regain those 14GB? If it is 100MB or so I would not complain, but 14GB is a lot of space.

You could have reserved space for super-users.
This can be disabled via tune2fs -m 0 /dev/whatever - but the default for that would be 5%, and that doesn't really fit.

The partition does not only need to hold your data but also metadata (inodes!).
14GB used on a 1TB disk seems reasonable if you formated it with the default options.
If you are sure inodes are not a problem, you can try to reformat with the option mkfs.ext4 -T largefile (or largefile4) and see if it helps.