Upgrading in the FULL recovery model requires more log and disk space than a traditional upgrade using the SIMPLE recovery ...

Upgrading in the FULL recovery model requires more log and disk space than a traditional upgrade using the SIMPLE recovery model. For further guidance around upgrading database farms in the FULL recovery model, visit http://go.microsoft.com/fwlink/?LinkId=280026. If you would prefer to upgrade using the SIMPLE recovery model, remove your databases from the appropriate feature and then restart the Upgrade wizard. Once the upgrade is complete the feature may be re-enabled.