运行mongorestore失败，以前从未发生过。这次我在两个节点副本配置的主服务器上进行恢复：
bash-4.1$ mongorestore mas
connected to: 127.0.0.1
2015-01-16T02:01:50.692-0500 mas/app.bson
2015-01-16T02:01:50.692-0500 going into namespace [mas.app]
1 objects found
2015-01-16T02:01:50.692-0500 Creating index: { key: { _id: 1 }, name: "_id_", ns: "mas.app" }
Error creating index mas.app: 18825 err: "couldn't create file /mongoDB-data/mas.ns"
Aborted
df -h的结果显示仍有很多空格：
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 50G 3.2G 44G 7% /
tmpfs 3.6G 0 3.6G 0% /dev/shm
/dev/xvdb 50G 4.4G 43G 10% /mongoDB-data
/mongoDB-data中的原始文件：
bash-4.1$ ls -l /mongoDB-data/
total 4356132
drwxr-xr-x. 2 mongod mongod 4096 Jan 16 01:42 journal
-rw-------. 1 mongod mongod 67108864 Jan 16 01:42 local.0
-rw-------. 1 mongod mongod 2146435072 Sep 4 20:06 local.1
-rw-------. 1 mongod mongod 2146435072 Sep 4 20:06 local.2
-rw-------. 1 mongod mongod 16777216 Jan 16 01:42 local.ns
drwx------. 2 root root 16384 Sep 17 01:49 lost+found
-rwxr-xr-x. 1 mongod mongod 6 Jan 16 01:42 mongod.lock
-rw-------. 1 mongod mongod 67108864 Sep 4 20:06 test.0
-rw-------. 1 mongod mongod 16777216 Sep 4 20:06 test.ns