[
https://issues.apache.org/jira/browse/HDFS-5950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13921634#comment-13921634
]
Chris Nauroth commented on HDFS-5950:
-------------------------------------
I believe this is an incompatible change, because there is now a requirement
that /dev/shm is writable for users of short-circuit reads. This was not a
requirement in prior releases, so it could break existing deployments where
/dev/shm is not writable.
I believe /dev/shm is often world-writable, but I've also seen system
administrators choose to restrict it as a hardening measure. I've come across
one user in internal testing here that encountered unexpected failures, because
/dev/shm was not writable.
> The DFSClient and DataNode should use shared memory segments to communicate
> short-circuit information
> -----------------------------------------------------------------------------------------------------
>
> Key: HDFS-5950
> URL: https://issues.apache.org/jira/browse/HDFS-5950
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, hdfs-client
> Affects Versions: 2.4.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Fix For: 2.4.0
>
> Attachments: HDFS-5950.001.patch, HDFS-5950.003.patch,
> HDFS-5950.004.patch, HDFS-5950.006.patch, HDFS-5950.007.patch,
> HDFS-5950.008.patch
>
>
> The DFSClient and DataNode should use the shared memory segments and unified
> cache added in the other HDFS-5182 subtasks to communicate short-circuit
> information.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
