I've been using Time Machine on this setup. So far it hasn't complained. But I also haven't had need to restore yet. As for power consumption, I unfortunately

I've been using Time Machine on this setup. So far it hasn't complained. But I also haven't had need to restore yet. As for power consumption, I unfortunately haven't kept tabs on the electricity nor have a Kill-a-Watt. But I have told FreeNAS to pretty aggressively spin down unused drives.