I am running mongodb on version 3.2.6 , ubuntu 14.04.4. One day my office was power outage, after that my mongod could not start.
The error like this:
···
test
···
klg@koala:~$ tail /var/log/mongodb/wiredtiger_spider.log
2016-08-24T19:15:51.487+0800 I CONTROL [initandlisten] options: { config: "/etc/mongodb/mongodb_spider.conf.bak", net:

{ port: 17017 }

, processManagement:

{ fork: true, pidFilePath: "/tmp/mongo_17017.pid" }

, storage: { dbPath: "/var/lib/mongodb/wiredtiger_spider", directoryPerDB: true, engine: "wiredTiger", journal:

{ enabled: true }

}, systemLog:

{ destination: "file", logAppend: true, path: "/var/log/mongodb/wiredtiger_spider.log", verbosity: 1 }

}
2016-08-24T19:15:51.487+0800 D NETWORK [initandlisten] fd limit hard:4096 soft:1024 max conn: 819
2016-08-24T19:15:51.516+0800 I STORAGE [initandlisten] wiredtiger_open config: create,cache_size=18G,session_max=20000,eviction=(threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),
2016-08-24T19:15:51.525+0800 E STORAGE [initandlisten] WiredTiger (-31802) [1472037351:525304][49250:0x7fc335dcecc0], file:WiredTiger.wt, connection: unable to read root page from file:WiredTiger.wt: WT_ERROR: non-specific WiredTiger error
2016-08-24T19:15:51.525+0800 E STORAGE [initandlisten] WiredTiger (0) [1472037351:525367][49250:0x7fc335dcecc0], file:WiredTiger.wt, connection: WiredTiger has failed to open its metadata
2016-08-24T19:15:51.525+0800 E STORAGE [initandlisten] WiredTiger (0) [1472037351:525379][49250:0x7fc335dcecc0], file:WiredTiger.wt, connection: This may be due to the database files being encrypted, being from an older version or due to corruption on disk
2016-08-24T19:15:51.525+0800 E STORAGE [initandlisten] WiredTiger (0) [1472037351:525391][49250:0x7fc335dcecc0], file:WiredTiger.wt, connection: You should confirm that you have opened the database with the correct options including all encryption and compression options
2016-08-24T19:15:51.526+0800 I - [initandlisten] Assertion: 28595:-31802: WT_ERROR: non-specific WiredTiger error
2016-08-24T19:15:51.558+0800 I STORAGE [initandlisten] exception in initAndListen: 28595 -31802: WT_ERROR: non-specific WiredTiger error, terminating
2016-08-24T19:15:51.558+0800 I CONTROL [initandlisten] dbexit: rc: 100