If you are attempting to perform a patch install on XenServer, but you run into the message "backup of the patch already exists," this is an easy fix. Most likely you or someone else tried to perform the patch install but it failed for some reason. This article shows you how to remove the patch backup.
Either use putty or some other method to gain access to the CLI of the XenServer in question.
Run the command xe patch-list name-label=enterTheNameOfThePatch to find the UUID of the patch you are attempting to install.
Enter the following command cd /opt/xensource/patch-backup/ and list the contents using the ls command.
Enter the following command to remove the patch in question rm -rf /patchUUIDFromStep2.
Try installing the patch again.
xe patch-list name-label=enterTheNameOfThePatch
rm -rf /patchUUIDFromStep2