We just added a 700 GB drive to one of our cloud servers and we ran into a horrible problem. We couldn't use 5% of it.

Normally, this isn't a problem because who really uses 95% of there drive but this particular server is used to store long term backups of STAGES so we need every byte. In order to fix this you can run the following command so it only reserves 1% of the drive:

tune2fs -m 1 /dev/sdaa

Where /deve/sdaa is the newly added drive.