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From mi...@apache.org
Subject hbase git commit: HBASE-13023 Document MultiWAL
Date Mon, 09 Mar 2015 03:58:28 GMT
Repository: hbase
Updated Branches:
  refs/heads/master 7642ee49f -> bde2d3067

HBASE-13023 Document MultiWAL

Project: http://git-wip-us.apache.org/repos/asf/hbase/repo
Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/bde2d306
Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/bde2d306
Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/bde2d306

Branch: refs/heads/master
Commit: bde2d306764addcd0f859ac79ca2b259c62d7a6a
Parents: 7642ee4
Author: Misty Stanley-Jones <mstanleyjones@cloudera.com>
Authored: Thu Feb 12 15:05:12 2015 +1000
Committer: Misty Stanley-Jones <mstanleyjones@cloudera.com>
Committed: Mon Mar 9 13:58:15 2015 +1000

 src/main/asciidoc/_chapters/architecture.adoc | 23 ++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/main/asciidoc/_chapters/architecture.adoc b/src/main/asciidoc/_chapters/architecture.adoc
index 6de7208..5dc244b 100644
--- a/src/main/asciidoc/_chapters/architecture.adoc
+++ b/src/main/asciidoc/_chapters/architecture.adoc
@@ -910,6 +910,29 @@ The WAL resides in HDFS in the _/hbase/WALs/_ directory (prior to HBase
0.94, th
 For more general information about the concept of write ahead logs, see the Wikipedia link:http://en.wikipedia.org/wiki/Write-ahead_logging[Write-Ahead
Log] article.
+==== MultiWAL
+With a single WAL per RegionServer, the RegionServer must write to the WAL serially, because
HDFS files must be sequential. This causes the WAL to be a performance bottleneck.
+HBase 1.0 introduces support MultiWal in link:https://issues.apache.org/jira/browse/HBASE-5699[HBASE-5699].
MultiWAL allows a RegionServer to write multiple WAL streams in parallel, by using multiple
pipelines in the underlying HDFS instance, which increases total throughput during writes.
This parallelization is done by partitioning incoming edits by their Region. Thus, the current
implementation will not help with increasing the throughput to a single Region.
+RegionServers using the original WAL implementation and those using the MultiWAL implementation
can each handle recovery of either set of WALs, so a zero-downtime configuration update is
possible through a rolling restart.
+.Configure MultiWAL
+To configure MultiWAL for a RegionServer, set the value of the property `hbase.wal.provider`
to `multiwal` by pasting in the following XML:
+  <name>hbase.wal.provider</name>
+  <value>multiwal</value>
+Restart the RegionServer for the changes to take effect. 
+To disable MultiWAL for a RegionServer, unset the property and restart the RegionServer.
 ==== WAL Flushing

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