I would like to run freenas on a HP P410 hardware RAID 5 4x600GB 15k SAS array and be alerted in the case of physical disk failure, however the freenas documentation says:
to prevent problems, do not enable the S.M.A.R.T. service if your disks are controlled by a RAID controller as it is the job of the controller to monitor S.M.A.R.T. and mark drives as Predictive Failure when they trip.
As the machine is installed in a lights-out data center, there's no way for the controller to alert anyone of RAID array being degraded. S.M.A.R.T. would appear to be an option - perhaps a physical disk failure would show as a high "Reallocated Sectors Count" at the array level?
Notes: Other options I have considered, but rejected are: Using a dumb HP H220 HBA with RAID-Z (<1.2TB guaranteed) or RAID 10 (1.2TB), but neither provide the capacity of RAID 5 (1.8TB), and I don't have any spare drive bays (HP DL120 G7). Also, there doesn't appear to be an HP agent for BSD. Context: I have a pair of these servers to reconfigure (main and replicated - 8 disks total) and they provide for an SQLServer and other VMs via iSCSI.
Update: I'm going down the cciss route (here's how I installed cciss on FreeNAS 9.x). Other possibility: RAID controller with out-of-band management on ethernet.
You really can't monitor the array status that well on your platform. One tacky option is cciss_vol_status, but it's far from the mainstream approach.
This is kind of a bad combination of hardware and software. FreeBSD ProLiant support is a bit Meh... Okay, it's actually worse than that...
So a few things to consider:
I'd either ditch FreeNAS if you insist on using hardware RAID or use a more ZFS-friendly SAS controller (LSI 9211) or give up the monitoring of the hardware RAID.
The way you would normally monitor this is with the HP software and agents.
Unless you can install this software on FreeNAS you may be out of luck. This ultimately falls down to the hardware not being fully supported for various reasons (not important in this discussion)