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https://issues.apache.org/jira/browse/HDFS-1848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13022905#comment-13022905
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Bharath Mundlapudi commented on HDFS-1848:
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Thanks Eli for explaining on the usecase. I briefly talked to Koji about this
Jira.
Some more thoughts on this.
1. If fs.data.dir.critical is not defined, then implementation should fall back
to existing tolerate a volume failure case.
2. If fs.data.dir.critical is defined, then fail-fast and fail-stop as you
described.
Case 2 you mentioned is interesting too. Today, datanode is not aware of this
case since it may not be part of the dfs.data.dir config.
I see that the key benefit of having this Jira is fail-fast. Meaning, if any of
the critical volume(s) fail, we let the namenode know immediately and datanode
will exit. So the replication will be taken care and cluster/datanode restarts
might see less issues with missing blocks.
W.r.t case 2 you mentioned, there are the possibilites of failures, right?
1. Data is stored on root partition disk say /root/hadoop (binaries,conf,log),
/root/data0
Failures: /root readonly filesystem or failure, /root/data0 readonly filesystem
or failure, complete disk0 failure.
2. Data NOT stored on root partition disk, /root(disk1), /data0(disk2)
Failures: /root readonly filesystem or failure, /data0(disk2) readonly
filesystem or failure.
3. Swap partition failure
How will this be detected?
I am wondering, if datanode should worry about all these issues regarding its
health or should a
configuration like in TaskTracker for health check script which will let
Datanode about the disk issues,
network issues etc is a better option?
> Datanodes should shutdown when a critical volume fails
> ------------------------------------------------------
>
> Key: HDFS-1848
> URL: https://issues.apache.org/jira/browse/HDFS-1848
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node
> Reporter: Eli Collins
> Fix For: 0.23.0
>
>
> A DN should shutdown when a critical volume (eg the volume that hosts the OS,
> logs, pid, tmp dir etc.) fails. The admin should be able to specify which
> volumes are critical, eg they might specify the volume that lives on the boot
> disk. A failure in one of these volumes would not be subject to the threshold
> (HDFS-1161) or result in host decommissioning (HDFS-1847) as the
> decommissioning process would likely fail.
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