[
https://issues.apache.org/jira/browse/HDFS-13788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16578168#comment-16578168
]
Zsolt Venczel commented on HDFS-13788:
--------------------------------------
Thanks [~xiaochen] for reporting this issue and thanks [~knanasi] for working
on the patch.
The updated documentation seems to be fine. +1 (non-binding) from me.
> Update EC documentation about rack fault tolerance
> --------------------------------------------------
>
> Key: HDFS-13788
> URL: https://issues.apache.org/jira/browse/HDFS-13788
> Project: Hadoop HDFS
> Issue Type: Task
> Components: documentation, erasure-coding
> Affects Versions: 3.0.0
> Reporter: Xiao Chen
> Assignee: Kitti Nanasi
> Priority: Major
> Attachments: HDFS-13788.001.patch
>
>
> From
> http://hadoop.apache.org/docs/r3.0.0/hadoop-project-dist/hadoop-hdfs/HDFSErasureCoding.html:
> {quote}
> For rack fault-tolerance, it is also important to have at least as many racks
> as the configured EC stripe width. For EC policy RS (6,3), this means
> minimally 9 racks, and ideally 10 or 11 to handle planned and unplanned
> outages. For clusters with fewer racks than the stripe width, HDFS cannot
> maintain rack fault-tolerance, but will still attempt to spread a striped
> file across multiple nodes to preserve node-level fault-tolerance.
> {quote}
> Theoretical minimum is 3 racks, and ideally 9 or more, so the document should
> be updated.
> (I didn't check timestamps, but this is probably due to
> {{BlockPlacementPolicyRackFaultTolerant}} isn't completely done when
> HDFS-9088 introduced this doc. Later there's also examples in
> {{TestErasureCodingMultipleRacks}} to test this explicitly.)
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
