query on zfs root pool

Hi
Following is the root zpool status


root@hslprd02-mgmt-app1:/# zpool status
  pool: BIrpool-2
 state: DEGRADED
status: One or more devices are unavailable in response to persistent errors.
        Sufficient replicas exist for the pool to continue functioning in a
        degraded state.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or 'fmadm repaired', or replace the device
        with 'zpool replace'.
        Run 'zpool status -v' to see device specific details.
  scan: resilvered 78.1M in 0h0m with 0 errors on Sat Aug 17 02:49:17 2013
config:

        NAME        STATE     READ WRITE CKSUM
        BIrpool-2   DEGRADED     0     0     0
          mirror-0  DEGRADED     0     0     0
            c2d0s0  ONLINE       0     0     0