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From st...@apache.org
Subject svn commit: r1213354 - /hbase/trunk/src/docbkx/configuration.xml
Date Mon, 12 Dec 2011 18:34:18 GMT
Author: stack
Date: Mon Dec 12 18:34:17 2011
New Revision: 1213354

URL: http://svn.apache.org/viewvc?rev=1213354&view=rev
HBASE-5000 Speed up simultaneous reads of a block when block caching is turned off; bit of
doc and why its a bad idea disabling block cache completely


Modified: hbase/trunk/src/docbkx/configuration.xml
URL: http://svn.apache.org/viewvc/hbase/trunk/src/docbkx/configuration.xml?rev=1213354&r1=1213353&r2=1213354&view=diff
--- hbase/trunk/src/docbkx/configuration.xml (original)
+++ hbase/trunk/src/docbkx/configuration.xml Mon Dec 12 18:34:17 2011
@@ -1551,6 +1551,14 @@ of all regions.
            <para>See <xref linkend="master.processes.loadbalancer" /> for more
information on the LoadBalancer.
+         <section xml:id="disabling.blockcache"><title>Disabling Blockcache</title>
+           <para>Do not turn off block cache (You'd do it by setting <varname>hbase.block.cache.size</varname>
to zero).
+           Currently we do not do well if you do this because the regionserver will spend
all its time loading hfile
+           indices over and over again.  If your working set it such that block cache does
you no good, at least
+           size the block cache such that hfile indices will stay up in the cache (you can
get a rough idea
+           on the size you need by surveying regionserver UIs; you'll see index block size
accounted near the
+           top of the webpage).</para>
+         </section>
       </section> <!--  important config -->

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