[
https://issues.apache.org/jira/browse/HDFS-1612?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tsz Wo (Nicholas), SZE updated HDFS-1612:
-----------------------------------------
Assignee: Joe Crobak
Hadoop Flags: [Reviewed]
> Note that this patch will get a -1 from hudson because it doesn't include any
> new tests. It's just a document update, though, so no new tests are expected.
The test-patch script actually is able to detect documentation changes. So it
won't get a -1 from not adding tests.
Obviously, the -1 core and contrib tests are not related to this.
+1 patch looks good.
> HDFS Design Documentation is outdated
> -------------------------------------
>
> Key: HDFS-1612
> URL: https://issues.apache.org/jira/browse/HDFS-1612
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: documentation
> Affects Versions: 0.20.2, 0.21.0
> Environment:
> http://hadoop.apache.org/hdfs/docs/current/hdfs_design.html#The+Persistence+of+File+System+Metadata
> http://hadoop.apache.org/common/docs/r0.20.2/hdfs_design.html#The+Persistence+of+File+System+Metadata
> Reporter: Joe Crobak
> Assignee: Joe Crobak
> Priority: Minor
> Attachments: HDFS-1612.patch
>
>
> I was trying to discover details about the Secondary NameNode, and came
> across the description below in the HDFS design doc.
> {quote}
> The NameNode keeps an image of the entire file system namespace and file
> Blockmap in memory. This key metadata item is designed to be compact, such
> that a NameNode with 4 GB of RAM is plenty to support a huge number of files
> and directories. When the NameNode starts up, it reads the FsImage and
> EditLog from disk, applies all the transactions from the EditLog to the
> in-memory representation of the FsImage, and flushes out this new version
> into a new FsImage on disk. It can then truncate the old EditLog because its
> transactions have been applied to the persistent FsImage. This process is
> called a checkpoint. *In the current implementation, a checkpoint only occurs
> when the NameNode starts up. Work is in progress to support periodic
> checkpointing in the near future.*
> {quote}
> (emphasis mine).
> Note that this directly conflicts with information in the hdfs user guide,
> http://hadoop.apache.org/common/docs/r0.20.2/hdfs_user_guide.html#Secondary+NameNode
> and
> http://hadoop.apache.org/hdfs/docs/current/hdfs_user_guide.html#Checkpoint+Node
> I haven't done a thorough audit of that doc-- I only noticed the above
> inaccuracy.
--
This message is automatically generated by JIRA.
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
