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HBASE-11939 Document Compressed Blockcache

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Misty Stanley-Jones 2014-11-17 13:56:51 +10:00
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src/main/docbkx/book.xml
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@ -2516,6 +2516,25 @@ rs.close();
</note>
</section>
</section>
<section>
<title>Comprewssed Blockcache</title>
<para><link xlink:href="https://issues.apache.org/jira/browse/HBASE-11331"
>HBASE-11331</link> introduced lazy blockcache decompression, more simply referred to
as compressed blockcache. When compressed blockcache is enabled. data and encoded data
blocks are cached in the blockcache in their on-disk format, rather than being
decompressed and decrypted before caching.</para>
<para xlink:href="https://issues.apache.org/jira/browse/HBASE-11331">For a RegionServer
hosting more data than can fit into cache, enabling this feature with SNAPPY compression
has been shown to result in 50% increase in throughput and 30% improvement in mean
latency while, increasing garbage collection by 80% and increasing overall CPU load by
2%. See HBASE-11331 for more details about how performance was measured and achieved.
For a RegionServer hosting data that can comfortably fit into cache, or if your workload
is sensitive to extra CPU or garbage-collection load, you may receive less
benefit.</para>
<para>Compressed blockcache is disabled by default. To enable it, set
<code>hbase.block.data.cachecompressed</code> to <code>true</code> in
<filename>hbase-site.xml</filename> on all RegionServers.</para>
</section>
</section>
<section