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From whe...@apache.org
Subject hadoop git commit: HDFS-8914. Document HA support in the HDFS HdfsDesign.md. Contributed by Lars Francke.
Date Mon, 23 Nov 2015 00:10:45 GMT
Repository: hadoop
Updated Branches:
  refs/heads/trunk f0cd90386 -> 0c7340f37

HDFS-8914. Document HA support in the HDFS HdfsDesign.md. Contributed by Lars Francke.

Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/0c7340f3
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/0c7340f3
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/0c7340f3

Branch: refs/heads/trunk
Commit: 0c7340f377f6663052be097ef58d60eee25f7334
Parents: f0cd903
Author: Haohui Mai <wheat9@apache.org>
Authored: Sun Nov 22 16:10:27 2015 -0800
Committer: Haohui Mai <wheat9@apache.org>
Committed: Sun Nov 22 16:10:27 2015 -0800

 hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt                     | 3 +++
 hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 106b569..41f5e7c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -2337,6 +2337,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9443. Disabling HDFS client socket cache causes logging message
     printed to console for CLI commands. (Chris Nauroth via wheat9)
+    HDFS-8914. Document HA support in the HDFS HdfsDesign.md.
+    (Lars Francke via wheat9)
 Release 2.7.3 - UNRELEASED

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md
index 4c0d44e..c779afc 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md
@@ -186,7 +186,7 @@ It is possible that a block of data fetched from a DataNode arrives corrupted.
 The FsImage and the EditLog are central data structures of HDFS. A corruption of these files
can cause the HDFS instance to be non-functional. For this reason, the NameNode can be configured
to support maintaining multiple copies of the FsImage and EditLog. Any update to either the
FsImage or EditLog causes each of the FsImages and EditLogs to get updated synchronously.
This synchronous updating of multiple copies of the FsImage and EditLog may degrade the rate
of namespace transactions per second that a NameNode can support. However, this degradation
is acceptable because even though HDFS applications are very data intensive in nature, they
are not metadata intensive. When a NameNode restarts, it selects the latest consistent FsImage
and EditLog to use.
-The NameNode machine is a single point of failure for an HDFS cluster. If the NameNode machine
fails, manual intervention is necessary. Currently, automatic restart and failover of the
NameNode software to another machine is not supported.
+Another option to increase resilience against failures is to enable High Availability using
multiple NameNodes either with a [shared storage on NFS](./HDFSHighAvailabilityWithNFS.html)
or using a [distributed edit log](./HDFSHighAvailabilityWithQJM.html) (called Journal). The
latter is the recommended approach.
 ### Snapshots

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