我的一个在AWS ec2 Ubuntu 16.04实例上运行的大小约为250GB的mongodb实例崩溃了。我可以在mongo日志中看到以下内容：
2018-08-13T14:47:42.506+0530 W - [initandlisten] Detected unclean shutdown - /var/lib/mongodb/mongod.lock is not empty.
2018-08-13T14:48:59.396+0530 I CONTROL [main] ***** SERVER RESTARTED *****
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] Block Cache Size GB: 1
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] Compression: snappy
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] MaxWriteMBPerSec: 1024
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] Engine custom option:
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] Crash safe counters: 0
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] Counters: 1
2018-08-13T14:48:59.416+0530 I STORAGE [main] [RocksDB] Use SingleDelete in index: 0
2018-08-13T14:48:59.441+0530 I ACCESS [main] Initialized External Auth Session
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] MongoDB starting : pid=9886 port=3308 dbpath=/var/lib/mongodb 64-bit host=Mongo-SortDB
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] db version v3.4.3-1.3
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] git version: de6b0610c550c8b217d598c2e405e6b5a307945d
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] OpenSSL version: OpenSSL 1.0.2g 1 Mar 2016
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] allocator: tcmalloc
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] modules: none
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] build environment:
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] distarch: x86_64
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] target_arch: x86_64
2018-08-13T14:48:59.443+0530 I CONTROL [initandlisten] options: { config: "/etc/mongod.conf", net: { bindIp: "x.x.x.x", port: 3308 }, processManagement: { fork: true, pidFilePath: "/var/run/mongod.pid" }, security: { authorization: "enabled" }, storage: { dbPath: "/var/lib/mongodb", engine: "rocksdb", journal: { enabled: true }, rocksdb: { cacheSizeGB: 1, compression: "snappy", counters: true, crashSafeCounters: false, maxWriteMBPerSec: 1024, singleDeleteIndex: false } }, systemLog: { destination: "file", logAppend: true, path: "/var/log/mongodb/mongod.log" } }
2018-08-13T14:48:59.443+0530 W - [initandlisten] Detected unclean shutdown - /var/lib/mongodb/mongod.lock is not empty.
如果我执行mongod --repair，它将需要多少时间和可用磁盘空间？