Some of the best advice I can give is this...
Read the forum rules and take some of it to heart. You will more than likely have a question and you may not realize this but sometimes the hardware/software you are running makes a difference on how the question is answered. Either create a tagline with your hardware listed or every time you ask for some help, include your system specs. You will get a much quicker response.
Lastly, before asking a question perform a Google search like "freenas scrub fails" or if you have something which might not be just FreeNAS related but FreeBSD (what FreeNAS is based on), search "freebsd scrub fails". Okay, that was a poor example but you get the point. A Google search is much better than a search using the Forum search engine.
There is a lot of free advice and help here and we are all willing participants.
And Welcome to the forums and FreeNAS.