Why are duplicate hosts appearing in PERF after failover? Why do some hosts resolve as "unqualified" while others resolve as "qualified" and have a domain name?

In mixed Windows cluster environments (where a cluster contains Windows and UNIX/Linux hosts), host name resolution issues may arise when Windows Internet Name Service (WINS) is used along with Domain Name Services (DNS). Note that WINS is enabled by default in all Windows installations.

Host names resolved on EGO cluster hosts running on Windows Server are resolved using WINS, while the same host names resolved on UNIX/Linux EGO cluster hosts are resolved using DNS. The difference is that WINS resolutions are NetBIOS names, which do not have a DNS suffix. This can create conflicts when host "hostA" is resolved as "HOSTA" using WINS, and "hostA.domain.com" on another cluster host using DNS.

We strongly recommend disabling WINS on all hosts in a mixed Windows cluster environments, but particularly on master candidate hosts. You can disable WINS under Advanced TCP/IP Settings in the Windows Control Panel by changing the NetBIOS setting to Disable NetBIOS over TCP/IP.

Find WINS information from Microsoft here: http://technet2.microsoft.com/WindowsServer/en/library/babc5a09-0561-44a5-884c-d2dfaa5b10191033.mspx?mfr=true