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Subject svn commit: r860400 - in /websites/production/activemq/content: cache/main.pageCache leveldb-store.html
Date Tue, 30 Apr 2013 15:21:29 GMT
Author: buildbot
Date: Tue Apr 30 15:21:29 2013
New Revision: 860400

Production update by buildbot for activemq


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 @@
         <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=""
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="" rel="nofollow">LevelDB</a><br
+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
+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">
 <h2><a shape="rect" name="LevelDBStore-Configuration"></a>Configuration</h2>

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