每次启动MongoDB时总是会收到如下 Unclean shutdown 提示，总结了一下出现该问题的原因及解决方法。
提示如下：
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D:\GREENT~1\PowerCmd>mongod --auth -dbpath C:\mongo\MongoDB\mongo\data
Wed May 16 16:06:50
Wed May 16 16:06:50 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability.
Wed May 16 16:06:50
Wed May 16 16:06:50 [initandlisten] MongoDB starting : pid=5016 port=27017 dbpath=C:\mongo\MongoDB\mongo\data 32-bit host=mxh
Wed May 16 16:06:50 [initandlisten]
Wed May 16 16:06:50 [initandlisten] ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data
Wed May 16 16:06:50 [initandlisten] ** see http://blog.mongodb.org/post/137788967/32-bit-limitations
Wed May 16 16:06:50 [initandlisten] ** with --journal, the limit is lower
Wed May 16 16:06:50 [initandlisten]
Wed May 16 16:06:50 [initandlisten] db version v2.0.1, pdfile version 4.5
Wed May 16 16:06:50 [initandlisten] git version: 3a5cf0e2134a830d38d2d1aae7e88cac31bdd684
Wed May 16 16:06:50 [initandlisten] build info: windows (5, 1, 2600, 2, 'Service Pack 3') BOOST_LIB_VERSION=1_42
Wed May 16 16:06:50 [initandlisten] options: { auth: true, dbpath: "C:\mongo\MongoDB\mongo\data" }
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Unclean shutdown detected.
Please visit http://dochub.mongodb.org/core/repair for recovery instructions.
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Wed May 16 16:06:51 [initandlisten] exception in initAndListen: 12596 old lock file, terminating
Wed May 16 16:06:51 dbexit:
Wed May 16 16:06:51 [initandlisten] shutdown: going to close listening sockets...
Wed May 16 16:06:51 [initandlisten] shutdown: going to flush diaglog...
Wed May 16 16:06:51 [initandlisten] shutdown: going to close sockets...
Wed May 16 16:06:51 [initandlisten] shutdown: waiting for fs preallocator...
Wed May 16 16:06:51 [initandlisten] shutdown: closing all files...
Wed May 16 16:06:51 [initandlisten] closeAllFiles() finished
Wed May 16 16:06:51 dbexit: really exiting now
经过多次测试发现，造成这种情况的原因是我使用PowerCMD启动MongoDB之后直接关掉PowerCMD窗口之后造成的，如果在关闭PowerCMD窗口之前使用 [ctrl + c] 快捷键终止mongod的运行也不会出现此种情况。而且，使用普通的CMD窗口运行mongo命令即使直接关掉窗口也不会出现该问题，看来还是使用原生程序更靠谱。
发生了此种情况解决方法也很简单，使用如下参数repair即可：
mongod --auth -dbpath C:\mongo\MongoDB\mongo\data --repair
然后重新启动即可：
D:\GREENT~1\PowerCmd>mongod --auth -dbpath C:\mongo\MongoDB\mongo\data
Wed May 16 16:44:35
Wed May 16 16:44:35 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability.
Wed May 16 16:44:35
Wed May 16 16:44:35 [initandlisten] MongoDB starting : pid=9616 port=27017 dbpath=C:\mongo\MongoDB\mongo\data 32-bit host=mxh
Wed May 16 16:44:35 [initandlisten]
Wed May 16 16:44:35 [initandlisten] ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data
Wed May 16 16:44:35 [initandlisten] ** see http://blog.mongodb.org/post/137788967/32-bit-limitations
Wed May 16 16:44:35 [initandlisten] ** with --journal, the limit is lower
Wed May 16 16:44:35 [initandlisten]
Wed May 16 16:44:35 [initandlisten] db version v2.0.1, pdfile version 4.5
Wed May 16 16:44:35 [initandlisten] git version: 3a5cf0e2134a830d38d2d1aae7e88cac31bdd684
Wed May 16 16:44:35 [initandlisten] build info: windows (5, 1, 2600, 2, 'Service Pack 3') BOOST_LIB_VERSION=1_42
Wed May 16 16:44:35 [initandlisten] options: { auth: true, dbpath: "C:\mongo\MongoDB\mongo\data" }
Wed May 16 16:44:35 [initandlisten] waiting for connections on port 27017
Wed May 16 16:44:35 [websvr] admin web console waiting for connections on port 28017
还有一些情况会造成这种 Unclean shutdown，解决方法可参考官方文档：
http://www.mongodb.org/display/DOCS/Durability+and+Repair