From b45071a8d0ca9a419e1936bd7e9583fdb384f06b Mon Sep 17 00:00:00 2001
From: Doug Meil <dmeil@apache.org>
Date: Thu, 16 Feb 2012 21:56:57 +0000
Subject: [PATCH] hbase-5397.  performance.xml, configuration.xml - correction
 to ZK config.

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1245199 13f79535-47bb-0310-9956-ffa450edef68
---
 src/docbkx/configuration.xml | 13 ++++++++++---
 src/docbkx/performance.xml   |  7 ++++++-
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/docbkx/configuration.xml b/src/docbkx/configuration.xml
index fff447835cf..44936e19e98 100644
--- a/src/docbkx/configuration.xml
+++ b/src/docbkx/configuration.xml
@@ -659,9 +659,16 @@ stopping hbase...............</programlisting> Shutdown can take a moment to
                 only but in production it is recommended that you run a
                 ZooKeeper ensemble of 3, 5 or 7 machines; the more members an
                 ensemble has, the more tolerant the ensemble is of host
-                failures. Also, run an odd number of machines. There can be no
-                quorum if the number of members is an even number. Give each
-                ZooKeeper server around 1GB of RAM, and if possible, its own
+                failures. Also, run an odd number of machines. In ZooKeeper, 
+                an even number of peers is supported, but it is normally not used 
+                because an even sized ensemble requires, proportionally, more peers 
+                to form a quorum than an odd sized ensemble requires. For example, an 
+                ensemble with 4 peers requires 3 to form a quorum, while an ensemble with 
+                5 also requires 3 to form a quorum. Thus, an ensemble of 5 allows 2 peers to 
+                fail, and thus is more fault tolerant than the ensemble of 4, which allows 
+                only 1 down peer.                 
+                </para>
+                <para>Give each ZooKeeper server around 1GB of RAM, and if possible, its own
                 dedicated disk (A dedicated disk is the best thing you can do
                 to ensure a performant ZooKeeper ensemble). For very heavily
                 loaded clusters, run ZooKeeper servers on separate machines
diff --git a/src/docbkx/performance.xml b/src/docbkx/performance.xml
index 39c2121a7e1..3ae84323269 100644
--- a/src/docbkx/performance.xml
+++ b/src/docbkx/performance.xml
@@ -188,7 +188,12 @@
     </section>
 
   </section>
-
+  <section xml:id="perf.zookeeper">
+    <title>ZooKeeper</title>
+    <para>See <xref linkend="zookeeper"/> for information on configuring ZooKeeper, and see the part
+    about having a dedicated disk.
+    </para>
+  </section>
   <section xml:id="perf.schema">
       <title>Schema Design</title>