T4 server running Solaris 11.3 , with a failed disk in mirrored rpool

Hi

We have a failed disk in a mirrored rpool.

T4 server has 4 internal disk , So we could use another disk to mirror too.

#zpool status rpool

 pool: rpool

 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'.

 scan: resilvered 77.6G in 10m30s with 0 errors on Thu Oct 31 00:03:05 2013

config:

   NAME             STATE   READ WRITE CKSUM

    rpool            DEGRADED   0   0   0