Repository: hadoop Updated Branches: refs/heads/branch-2 812dbea5c -> 049ccf71c
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/049ccf71 Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/049ccf71 Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/049ccf71 Branch: refs/heads/branch-2 Commit: 049ccf71ce4457296974f12f5159540f8fcf1ede Parents: 812dbea Author: Haohui Mai <[email protected]> Authored: Sun Nov 22 16:10:27 2015 -0800 Committer: Haohui Mai <[email protected]> Committed: Sun Nov 22 16:10:38 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(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/hadoop/blob/049ccf71/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt ---------------------------------------------------------------------- diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt index 5d77664..be90287 100644 --- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt +++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt @@ -1482,6 +1482,9 @@ 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 INCOMPATIBLE CHANGES http://git-wip-us.apache.org/repos/asf/hadoop/blob/049ccf71/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md ---------------------------------------------------------------------- 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 e0e2c4c..5fcae3a 100644 --- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md +++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md @@ -185,7 +185,7 @@ It is possible that a block of data fetched from a DataNode arrives corrupted. T 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
