# metainit -s blue d11 1 1 c1t6d0s0
blue/d11: Concat/Stripe is setup
# metainit -s blue d12 1 1 c2t6d0s0
blue/d12: Concat/Stripe is setup
# metainit -s blue d10 -m d11           
blue/d10: Mirror is setup
# metattach -s blue d10 d12
blue/d10: submirror blue/d12 is attached

# metastat -s blue
blue/d10: Mirror
    Submirror 0: blue/d11
      State: Okay         
    Submirror 1: blue/d12
      State: Resyncing    
    Resync in progress: 0 % done
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 17674902 blocks

blue/d11: Submirror of blue/d10
    State: Okay         
    Size: 17674902 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Reloc  Hot Spare
        c1t6d0s0                   0     No    Okay                


blue/d12: Submirror of blue/d10
    State: Resyncing    
    Size: 17674902 blocks
    Stripe 0:
        Device              Start Block  Dbase State        Reloc  Hot Spare
        c2t6d0s0                   0     No    Okay