svn commit: r860400 - in /websites/production/activemq/content: cache/main.pageCache leveldb-store.html

[buildbot]

Author: buildbot
Date: Tue Apr 30 15:21:29 2013
New Revision: 860400

Log:
Production update by buildbot for activemq

Modified:
    websites/production/activemq/content/cache/main.pageCache
    websites/production/activemq/content/leveldb-store.html

Modified: websites/production/activemq/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.

Modified: websites/production/activemq/content/leveldb-store.html
==============================================================================
--- websites/production/activemq/content/leveldb-store.html (original)
+++ websites/production/activemq/content/leveldb-store.html Tue Apr 30 15:21:29 
2013
@@ -72,8 +72,21 @@
         <tr>
         <td valign="top" width="100%">
           <div class="wiki-content maincontent">
+<div class="panelMacro"><table class="infoMacro"><colgroup span="1"><col 
span="1" width="24"><col span="1"></colgroup><tr><td colspan="1" rowspan="1" 
valign="top"><img align="middle" 
src="https://cwiki.apache.org/confluence/images/icons/emoticons/information.gif";
 width="16" height="16" alt="" border="0"></td><td colspan="1" 
rowspan="1"><b>Version Compatibility</b><br clear="none">Available in ActiveMQ 
5.8.0 and newer</td></tr></table></div>
+
 <p>LevelDB is a file based persistence database that is local to the message 
broker that is using it.<br clear="none">
-It has been optimized to provide even faster persistence than KahaDB.</p>
+It has been optimized to provide even faster persistence than KahaDB.  It's 
similar to KahahDB but <br clear="none">
+instead of using a custom B-Tree implementation to index the write ahead logs, 
it uses <a shape="rect" class="external-link" 
href="https://code.google.com/p/leveldb/"; rel="nofollow">LevelDB</a><br 
clear="none">
+based indexes which have several nice properties due to the 'append only' 
files access patterns : </p>
+
+<ul><li>Fast updates (No need to do random disk updates)</li><li>Concurrent 
reads</li><li>Fast index snapshots using hard links</li></ul>
+
+
+<p>Both KahaDB and the LevelDB store have to do periodic garbage collection 
cycles to determine which <br clear="none">
+log files can deleted.  In the case of KahaDB, this can be quite expensive as 
you increase<br clear="none">
+the amount of data stored and can cause read/write stalls while the collection 
occurs.  The LevelDB<br clear="none">
+store uses a much cheaper algorithm to determine when log files can be 
collected and avoids those<br clear="none">
+stalls.</p>
 
 <h2><a shape="rect" name="LevelDBStore-Configuration"></a>Configuration</h2>