https://jingyan.baidu.com/article/9f7e7ec055c4c86f28155435.html
http://pubs.vmware.com/vsphere-50/index.jsp?topic=%2Fcom.vmware.vsphere.monitoring.doc_50%2FGUID-8EF36D7D-59B6-4C74-B1AA-4A9D18AB6250.html
https://blog.csdn.net/zhouzhiwengang/article/details/26618521