When you use Xsan Admin to remove a metadata controller, all metadata controllers must be accessible to do so. In many an upgrade scenario this has turned out to be challenging. Therefore, you can remove a metadata controller using the configuration files. To do so, open /Library/Preferences/Xsan/fsnameservers.
In this file, you’ll see the IP address of all active metadata controllers that are used to manage any (or no) volumes as follows:
Remove the line with the IP address of the system you’ll be removing so it looks like the following, assuming you’re removing 192.168.210.2):
This needs to be repeated for all metadata controllers and clients. If you miss any clients, you’ll see a “fsnameservers incorrect” error in Xsan Admin for those clients. You can then edit the fsnameservers file for those clients or just remove them from the SAN and readd them back to clear the error. Once done, you can remove the metadata controllers from Xsan Admin, where they’ll still show up (even though they’re not functional as a metadata controller).
Once you’ve removed a metadata controller in this fashion, you’ll also need to uninstall and reinstall Xsan on the controller in order for the controller to just be a regular member of the SAN properly.