You receive message: Unsupported feature of the database platform you are using.

You can try with another driver, edit file: application/config/production/database.php

in line:

$db['mysql']['dbdriver'] = 'mysqli';

In this case for example change from mysqli to mysql

Also it’s safer if you backup via cpanel, so just backup there:

http://iwinter.com.hr/support/?p=3144

Stackoverflow link about this issue:

http://stackoverflow.com/questions/24197844/database-utility-backups-not-working-with-mysqli-codeignitor