Thank you. There are some good information in the link.
As I read and understand there are a few kind of logs in vSphere:
1) syslogs for hosts
2) logs ferom vCenter server components on ESi 5.1 (/var/log/vpxa.log and /var/log/fdm.log)
Are these two server components logs located at the below?
C:\ProgramData\VMware\VMware VirtualCenter\Logs