Clarify hbal man page

In the sense of hbal, and, in fact, all htools, drained nodes
are considered as offline. Also, the cluster score is not just
the sum of its component, but, e.g., the count of instances on
offline nodes is weighted stronger.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>

diff --git a/man/hbal.rst b/man/hbal.rst
index 766baac..4b1e5ef 100644 (file)
--- a/man/hbal.rst
+++ b/man/hbal.rst
@@ -91,7 +91,8 @@ At each step, we prevent an instance move if it would cause:
 
 - a node to go into N+1 failure state
 - an instance to move onto an offline node (offline nodes are either
-  read from the cluster or declared with *-O*)
+  read from the cluster or declared with *-O*; drained nodes are
+  considered offline)
 - an exclusion-tag based conflict (exclusion tags are read from the
   cluster and/or defined via the *\--exclusion-tags* option)
 - a max vcpu/pcpu ratio to be exceeded (configured via *\--max-cpu*)
@@ -102,15 +103,16 @@ CLUSTER SCORING
 ~~~~~~~~~~~~~~~
 
 As said before, the algorithm tries to minimise the cluster score at
-each step. Currently this score is computed as a sum of the following
-components:
+each step. Currently this score is computed as a weighted sum of the
+following components:
 
 - standard deviation of the percent of free memory
 - standard deviation of the percent of reserved memory
 - standard deviation of the percent of free disk
 - count of nodes failing N+1 check
 - count of instances living (either as primary or secondary) on
-  offline nodes
+  offline nodes; in the sense of hbal (and the other htools) drained
+  nodes are considered offline
 - count of instances living (as primary) on offline nodes; this
   differs from the above metric by helping failover of such instances
   in 2-node clusters