When running,

Code:
fallocate -l 10G /path/to/file
I'm returned the following error:

Code:
fallocate: file: fallocate failed: Operation not supported
Creating the file using dd (if=/dev/urandom) works, but if I'm trying to create large files, tens of GBs in size, it takes several hours to complete.

Running Ubuntu 14.04. Using an ext4 partition, specifying a file-type doesn't appear to alter the outcome.

Working fine on my CentOS machines, just not Ubuntu.