I have a family member who was moving their law firm over the weekend. I moved all the computers and what not. She has a NAS (running freenas) which has been moved as well. I got the error: This is a data disk and cannot boot. System halted. I'm quite concerned that we lost data. Already messed around with boot orders.
Tl;dr, nas won't boot after moving.
Make sure its booting to whatever disk is your boot media, whether that be a usb or a hard drive. You could try to boot it with all data disks disconnected just to see if the boot media still works. When it comes up with that error, your motherboard is trying to boot from a data disk.
Unplugging everything allowed it to boot. What then? Just reboot then plug in the drives?
Shut it off, and in the bios you need to set the boot usb as the highest item on the boot priority
Agree with @thecaveman.
Since you said you've already messed with the boot orders (presumably without sucess) it may be worth noting that there is a high probability that your data is intact, assuming the data disks haven't been damaged in anyway. It does sound like your boot media is jacked. If it were me I would try disconnecting your data disks, do a fresh install of FreeNAS to a new boot device of your choice (probably a USB Flash drive) then reattach your data disks. There's a high probability that you can import the pre-existing ZFS volumes. You'll lose shares and permissions you had before (unless you have a config backup you can import) but your data should be intact.
Hmm, that reply was to your first post. Sounds like you're on the right track.
Because he said this:
he should 100% just set the boot order correctly and try that, before he starts pissing about with a new install.
Agreed. No need for a fresh install now that he has it booting.
Yeah, basically that error means your freenas os is not 1. plugged in or 2. not the first boot media in the list.
Freenas is usually on a USB...which it should be.
Update: after unplugging the drives, the USB drive is now showing up in the boot menu properly. Problem solved.