Or you wanted to remove those non existing volumes which keep showing in your volumes list.
First, to unmap the volumes from your target you have to edit the following file and restart your iSCSI target service.
iscsi_settings.xml in: /opt/openfiler/etc/iscsi/targets
remove all ghost target, only from sub tag
Secondly, to remove the non existing volumes,
my volumes.xml from /opt/openfiler/etc/
The file should look like the below, remove