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Colin Patrick McCabe commented on HDFS-4453:
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bq. Regarding /var/lib/hadoop-hdfs vs /var/run/hadoop-hdfs – why's it problematic if /var/run
is a tmpfs? We shouldn't need it to persist cross-reboot, and /var/run is generally not cleaned
by a tmpwatch process. tmpfs is also better in that it will continue to work even if a local
disk dies.
If the /var/run/hadoop-hdfs directory gets removed, hdfs itself can't recreate it (you need
root permissions to create a directory in /var/run.) So after a reboot, things would probably
stop working.
> Make a simple doc to describe the usage and design of the shortcircuit read feature
> -----------------------------------------------------------------------------------
>
> Key: HDFS-4453
> URL: https://issues.apache.org/jira/browse/HDFS-4453
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, hdfs-client
> Reporter: Brandon Li
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-4453.001.patch, HDFS-4453.002.patch
>
>
> It would be nice to have a document to describe the configuration and design of this
feature. Also its relationship with previous short circuit read implementation(HDFS-2246),
for example, can they co-exist, or this one is planed to replaces HDFS-2246, or it can fall
back on HDFS-2246 when unix domain socket is not supported.
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