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Edit of SlabCache note 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1560228 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2014-01-22 00:39:57 +00:00
parent 028a00cc31
commit ff53d75330
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src/main/docbkx/upgrading.xml
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@ -333,13 +333,14 @@ The block size default size has been changed in 0.92.0 from 0.2 (20 percent of h
</para>
</section>
<section><title>Experimental off-heap cache
</title>
<section xml:id="slabcache"><title>Experimental off-heap cache: SlabCache</title>
<para>
A new cache was contributed to 0.92.0 to act as a solution between using the “on-heap” cache which is the current LRU cache the region servers have and the operating system cache which is out of our control.
To enable, set “-XX:MaxDirectMemorySize” in hbase-env.sh to the value for maximum direct memory size and specify hbase.offheapcache.percentage in hbase-site.xml with the percentage that you want to dedicate to off-heap cache. This should only be set for servers and not for clients. Use at your own risk.
See this blog post for additional information on this new experimental feature: http://www.cloudera.com/blog/2012/01/caching-in-hbase-slabcache/
To enable <emphasis>SlabCache</emphasis>, as this feature is being called, set “-XX:MaxDirectMemorySize” in hbase-env.sh to the value for maximum direct memory size and specify
<property>hbase.offheapcache.percentage</property> in <filename>hbase-site.xml</filename> with the percentage that you want to dedicate to off-heap cache. This should only be set for servers and not for clients. Use at your own risk.
See this blog post, <link xlink:href="http://www.cloudera.com/blog/2012/01/caching-in-hbase-slabcache/">Caching in Apache HBase: SlabCache</link>, for additional information on this new experimental feature.
</para>
<para>This feature has mostly been eclipsed in later HBases. See <link xlink:href="https://issues.apache.org/jira/browse/HBASE-7404 ">HBASE-7404 Bucket Cache:A solution about CMS,Heap Fragment and Big Cache on HBASE</link>, etc.</para>
</section>
<section><title>Changes in HBase replication