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HBASE-4091 book.xml - description of block cache in arch, description of inMemory in schema creation 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1151747 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2011-07-28 06:34:56 +00:00
parent d6c0338415
commit aaad75743a
1 changed files with 24 additions and 3 deletions
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src/docbkx/book.xml
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@ -261,6 +261,17 @@ admin.enableTable(table);
that includes versioning. Take that into consideration when making your design, as well as block size for the ColumnFamily. that includes versioning. Take that into consideration when making your design, as well as block size for the ColumnFamily.
</para> </para>
</section> </section>
<section xml:id="cf.in.memory">
<title>
In-Memory ColumnFamilies
</title>
<para>ColumnFamilies can optionally be defined as in-memory. Data is still persisted to disk, just like any other ColumnFamily.
In-memory blocks have the highest priority in the <xref linkend="block.cache" />, but it is not a guarantee that the entire table
will be in memory.
</para>
<para>See <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/HColumnDescriptor.html">HColumnDescriptor</link> for more information.
</para>
</section>
</chapter> </chapter>
@ -984,9 +995,19 @@ HTable table2 = new HTable(conf2, "myTable");</programlisting>
</para> </para>
</section> </section>
</section> <!-- store -->
</section>
<section xml:id="block.cache">
<title>Block Cache</title>
<para>The Block Cache contains three levels of block priority to allow for scan-resistance and in-memory ColumnFamilies. A block is added with an in-memory
flag if the containing ColumnFamily is defined in-memory, otherwise a block becomes a single access priority. Once a block is accessed again, it changes to multiple access.
This is used to prevent scans from thrashing the cache, adding a least-frequently-used element to the eviction algorithm. Blocks from in-memory ColumnFamilies
are the last to be evicted.
</para>
<para>
For more information, see the <link xlink:href="http://hbase.apache.org/xref/org/apache/hadoop/hbase/io/hfile/LruBlockCache.html">LruBlockCache source</link>
</para>
</section>
</section> </section>
<section xml:id="wal"> <section xml:id="wal">