You can enter engineering mode in Unisphere on an EMC array by holding down CTRL + ALT + SHIFT + F12. Enter the password messner. What does engineering mode get you? You’ll see additional storage groups such as ~management that may have straggler hosts connected to them.
I had an issue removing hosts from the hosts list in Unisphere. It turns out you have to enter engineering mode and remove the connections themselves. It’s a pain. After you enter engineering mode you can then navigate to your storage groups, select the one with the hosts attached and then click on connectivity status.
After that you have to select each link and de-register them one by one. I had 10 hosts in the list to de-register with 8 links each. 15 minutes I’d like back.