Repository: hbase Updated Branches: refs/heads/master 7335f5f87 -> 87e293bee
Add note on how to set up blockcache so we cache META blocks only and pull in DATA blocks on each access Project: http://git-wip-us.apache.org/repos/asf/hbase/repo Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/3cff0d34 Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/3cff0d34 Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/3cff0d34 Branch: refs/heads/master Commit: 3cff0d34c4171562b12e329a627944959a87acd9 Parents: 7335f5f Author: stack <[email protected]> Authored: Fri Aug 8 07:46:34 2014 -0700 Committer: stack <[email protected]> Committed: Fri Aug 8 07:46:34 2014 -0700 ---------------------------------------------------------------------- src/main/docbkx/book.xml | 13 +++++++++++++ 1 file changed, 13 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/hbase/blob/3cff0d34/src/main/docbkx/book.xml ---------------------------------------------------------------------- diff --git a/src/main/docbkx/book.xml b/src/main/docbkx/book.xml index 21e0af5..d0c6bfa 100644 --- a/src/main/docbkx/book.xml +++ b/src/main/docbkx/book.xml @@ -2137,6 +2137,19 @@ rs.close(); and would surely evict data that's currently in use. </para> </listitem> </itemizedlist> + <section xml:id="data.blocks.in.fscache"> + <title>Caching META blocks only (DATA blocks in fscache)</title> + <para>An interesting setup is one where we cache META blocks only and we read DATA + blocks in on each access. If the DATA blocks fit inside fscache, this alternative + may make sense when access is completely random across a very large dataset. + To enable this setup, alter your table and for each column family + set <varname>BLOCKCACHE => 'false'</varname>. You are 'disabling' the + BlockCache for this column family only you can never disable the caching of + META blocks. Since + <link xlink:href="https://issues.apache.org/jira/browse/HBASE-4683";>HBASE-4683 Always cache index and bloom blocks</link>, + we will cache META blocks even if the BlockCache is disabled. + </para> + </section> </section> <section xml:id="offheap.blockcache">
