Install of FreePBX custom HDD size

I would like to install FreePBX iso but I would like to choice my HDD setup is there anyway of doing this. Make long story short we I have been playing with Trixbox for a couple of weeks got Heartbeat and DRBD to work great with it, but looks like it is now dead. I would like to get Heartbeat and DRBD to work with FreePBX but I need to make some with setting partition on the hard drives.