How can I monitor HP P410 hardware RAID degraded in Freenas

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:

• ZFS is a software RAID and volume management solution engineered for use with raw SAS controllers and to bypass any form of hardware RAID.
• Hardware RAID can be used, but you lose some of the data protection features of ZFS.
• If you use hardware RAID with ZFS, be sure to do it on an OS/platform that allows you to monitor it!
• HP Smart Array controllers like the P410 are popular and well-supported under every other operating system out there. They present a block device to the OS comprised of the collection of underlying RAID devices.
• Smart Array controllers do not have a JBOD or passthrough mode. They are RAID-only.
• HP has tools and management agents to monitor hardware health and send SNMP and email alerts. Again, these won't work on your FreeNAS.
• S.M.A.R.T. is not the last word in storage monitoring!

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)