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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 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1213354 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2011-12-12 18:34:17 +00:00
parent 28ee3bf9ba
commit fe60d5dce8
1 changed files with 8 additions and 0 deletions
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src/docbkx/configuration.xml
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@ -1551,6 +1551,14 @@ of all regions.
<para>See <xref linkend="master.processes.loadbalancer" /> for more information on the LoadBalancer.
</para>
</section>
<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>
</section> <!-- important config -->