howto/ganeti: document where to find key infos

howto/ganeti.md

@@ -684,7 +684,17 @@ depending on the situation.
 
 Use this procedure before to a virtual disk from one of the iSCSI SANs.
 
-First, remove the multipath config and reload:
+First, we'll need to gather a some information about the disk to remove.
+
+ * Which SAN is hosting the disk
+ * What LUN is assigned to the disk
+ * The WWID of both the SAN and the virtual disk
+
+    /usr/local/sbin/tpo-show-san-disks
+    SMcli -n <san> -S -quick -c "show storageArray summary;" | grep "Storage array world-wide identifier"
+    cat /etc/multipath/conf.d/<name>.conf
+
+Second, remove the multipath config and reload:
 
     gnt-cluster command rm /etc/multipath/conf.d/test-01.conf
     gnt-cluster command "multipath -r ; multipath -w <disk-wwid> ; multipath -r"