found a better command to inspect per-node storage stats

tsa/howto/ganeti.mdwn

@@ -168,9 +168,9 @@ memory, and compare it with the node's capacity:
     watch -n5 -d 'gnt-instance list -o pnode,name,be/vcpus,be/memory,disk_usage,disk_template,status  |  sort; echo; gnt-node list'
 
 The latter does not show disk usage for secondary volume groups, for a
-complete picture of disk usage, try this:
+complete picture of disk usage, use:
 
-    gnt-cluster command vgs
+    gnt-node list-storage
 
 The [gnt-cluster verify](http://docs.ganeti.org/ganeti/2.15/man/gnt-cluster.html#verify) command will also check to see if there's
 enough space on secondaries to account for the failure of a