zpool status reports error ... what next?

Type zpool clear raid2 to clear the errors and initiate a scrub.

If the errors persist following that, replace the disk.

More details about the hardware would help, so this is generic advice. My recommendation for bunch of consumer disks connected to a PC motherboard are different than what I'd do for enterprise-level gear.

The tool tells you what you need to do: "Determine if the device needs to be replaced".

The tools are only so intelligent and need you, as the human administrator, to figure some things. The steps required are specific to your hardware and your set up, so you will need to make some decisions based on your knowledge of the system.

Take a look at the output from the command. It looks like device gptid/5fe33556-3ff2-11e2-9437-f46d049aaeca is experiencing 'WRITE' errors. '1.13M' is a very high error rate and I suspect the problem has been occurring for a while without you noticing. See if you can figure out why and then replace the disk.

If you have a hardware controller, that controller might have additional tools to help you determine the nature of the failure.

ZFS can deal with corrupt sectors, so there is no need to panic. But don't ignore the problem either.

As a preventative measure, you should also run a ZFS scrub regularly. See http://doc.freenas.org/index.php/ZFS_Scrubs . This will alert you when ZFS first encounters a problem, well before you hit the 1.13M mark.

Use the following command change out /dev/adaX for your drives.

[blackout@freenas ~]# smartctl -a /dev/ada0 | grep "Serial"
Serial Number: WD-WCC4EXXXXXXXX
also a helpful commant [blackout@freenas ~]# glabel status