[docs] Add an upgrade note about MM threads

Some users configure MM threads to high values to work around the fact that the MM was slow at scheduling tasks. This is now fixed in 1.4, so this patch adds a note about this. Change-Id: I5b9c36e04d24d0bc9991f19da35b29b474dd6022 Reviewed-on: http://gerrit.cloudera.org:8080/7283 Reviewed-by: Adar Dembo <[email protected]> Reviewed-by: Todd Lipcon <[email protected]> Tested-by: Jean-Daniel Cryans <[email protected]>
cutiechi · Jun 28, 2017 · 42a0749 · 42a0749
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diff --git a/docs/release_notes.adoc b/docs/release_notes.adoc
@@ -30,6 +30,15 @@
 
 [[rn_1.4.0]]
 
+[[rn_1.4.0_upgrade_notes]]
+== Upgrade Notes
+
+* The Maintenance Manager now fully uses the threads it's given (see the improvements
+  described further below), so it's now able to generate a lot more IO by flushing and
+  compacting more often. Generally, the recommended ratio of MM threads to data
+  directories is 1:3; operators of clusters above that ratio should be mindful of
+  this when upgrading.
+
 [[rn_1.4.0_new_features]]
 == New features