Index: src/docbkx/performance.xml
===================================================================
--- src/docbkx/performance.xml (revision 1245192)
+++ src/docbkx/performance.xml (working copy)
@@ -188,7 +188,12 @@
-
+
+ ZooKeeper
+ See for information on configuring ZooKeeper, and see the part
+ about having a dedicated disk.
+
+
Schema Design
Index: src/docbkx/configuration.xml
===================================================================
--- src/docbkx/configuration.xml (revision 1245192)
+++ src/docbkx/configuration.xml (working copy)
@@ -659,9 +659,16 @@
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.
+
+ 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