Verified this bug on rhev-hypervisor6-6.6-20141008.0.iso and ovirt-node-3.1.0-0.22.20141010git96b7ca3.el6
The data partition size is the disk free size as default now.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHEA-2015-0160.html