mongodb2.6.10单节点数据达到2TB就无法执行命令？

最近有台数据备份服务器，因为是备份机器，所以配置较低，如下：
centos6.3
内存:4G
硬盘：10TB EXT4
mongodb 2.6.10

在数据达到2TB时，在控制台执行命令就会报如下错误：
[conn1] ERROR: Uncaught std::exception: boost::filesystem::directory_iterator::construct: Too many open files: “/data/optlog”, terminating
2015-08-11T16:05:26.737+0800 [conn1] dbexit:
2015-08-11T16:05:26.737+0800 [conn1] shutdown: going to close listening sockets…
2015-08-11T16:05:26.737+0800 [conn1] closing listening socket: 8
2015-08-11T16:05:26.737+0800 [conn1] shutdown: going to flush diaglog…
2015-08-11T16:05:26.737+0800 [conn1] shutdown: going to close sockets…
2015-08-11T16:05:26.737+0800 [conn1] shutdown: waiting for fs preallocator…
2015-08-11T16:05:26.737+0800 [conn1] shutdown: lock for final commit…
2015-08-11T16:05:26.737+0800 [conn1] shutdown: final commit…
2015-08-11T16:05:26.746+0800 [initandlisten] now exiting
2015-08-11T16:05:26.747+0800 [initandlisten] dbexit: ; exiting immediately

不知有碰到过这种情况的朋友吗？