Unhealthy pool status.

root@freenas:~ # zpool status FREENASPOOL
  pool: FREENASPOOL
state: ONLINE
status: One or more devices has experienced an unrecoverable error.  An
        attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or replace the device with 'zpool replace'.
   see...