repair mongod db fail

[root@localhost mongodb]# service mongod status
mongod is stopped
[root@localhost mongodb]# service mongod start
Starting mongod: [FAILED]
[root@localhost mongodb]# tail -f mongod.log
2016-12-12T09:58:13.342+0700 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2016-12-12T09:58:13.342+0700 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2016-12-12T09:58:13.342+0700 I CONTROL [initandlisten]
2016-12-12T09:58:13.656+0700 I INDEX [initandlisten] found 2 index(es) that wasn't finished before shutdown
2016-12-12T09:58:13.656+0700 I - [initandlisten] Fatal assertion 28579 UnsupportedFormat: Unable to find metadata for table:index-1972--4952926493820669755 Index:

- version too new for this mongod. See http://dochub.mongodb.org/core/3.4-index-downgrade for detailed instructions on how to handle this error.
2016-12-12T09:58:13.656+0700 I - [initandlisten]