# metastat d200                                                                                                                                                                                    
  d200: Mirror
    Submirror 0: d201
      State: Needs maintenance         
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 209682432 blocks
  d201: Submirror of d200
    State: Okay         
    Size: 209682432 blocks
    Stripe 0:
        Device    Start Block  Dbase State        Hot Spare
        vpath9c          0     No    Last Erred         

Oops! It's a one-side mirror so one can't re-sync from the other side of the mirror. File system is consistent as it can be mounted (fsck shows no errors). SVM does not agree.

• Do a backup
• Umount the file system (in this case it was /oracle)
• Drop the mirror: metaclear -f d200
• recreate mirror: metainit d200 -m d201
• The maintance state is now OK:

# metastat d200                                                                                                                                                                                    
d200: Mirror
    Submirror 0: d201
      State: Okay         
    Pass: 1
    Read option: roundrobin (default)
    Write option: parallel (default)
    Size: 209682432 blocks
d201: Submirror of d200
    State: Okay         
    Size: 209682432 blocks
    Stripe 0:
        Device    Start Block  Dbase State        Hot Spare
        vpath9c          0     No    Okay         

http://francoisbasquin.blogspot.com/2008/06/solaris-metastat-need-maintenance-state.html