From 22bb923beb941821386e353d96f64912b53b1b8e Mon Sep 17 00:00:00 2001
From: Michael Stack <stack@apache.org>
Date: Thu, 28 Jul 2011 06:36:49 +0000
Subject: [PATCH] HBASE-4092 performance.xml - adding batch-loading entry for
 using deferred log flush

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1151749 13f79535-47bb-0310-9956-ffa450edef68
---
 src/docbkx/performance.xml | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/docbkx/performance.xml b/src/docbkx/performance.xml
index 2d8cdddf0cf..175297af613 100644
--- a/src/docbkx/performance.xml
+++ b/src/docbkx/performance.xml
@@ -199,7 +199,21 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
 }</programlisting>
   </para>
   </section>
-  </section>
+  <section xml:id="def.log.flush">
+  <title>
+  Table Creation: Deferred Log Flush
+  </title>
+<para>
+The default behavior for Puts using the Write Ahead Log (WAL) is that <classname>HLog</classname> edits will be written immediately.  If deferred log flush is used, 
+WAL edits are kept in memory until the flush period.  The benefit is aggregated and asynchronous <classname>HLog</classname>- writes, but the potential downside is that if
+ the RegionServer goes down the yet-to-be-flushed edits are lost.  This is safer, however, than not using WAL at all with Puts.
+</para>
+<para>
+Deferred log flush can be configured on tables via <link
+      xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/HTableDescriptor.html">HTableDescriptor</link>.  The default value of <varname>hbase.regionserver.optionallogflushinterval</varname> is 1000ms.
+</para>
+  </section>  
+  </section>  <!-- batch loading -->
 
   <section>
     <title>HBase Client</title>