[jira] [Commented] (HADOOP-14136) Default FS For ViewFS

["Erik Krogen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-14136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15890812#comment-15890812 ] 

Erik Krogen commented on HADOOP-14136:
--------------------------------------

[~andrew.wang], [~manojg] - pinging based off of previous involvement on related tickets. Also [~mingma] based on previous involvement with ViewFS.

> Default FS For ViewFS
> ---------------------
>
>                 Key: HADOOP-14136
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14136
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: fs, viewfs
>            Reporter: Erik Krogen
>
> It would be useful if ViewFS had the ability to designate one FileSystem as a "primary"/"default" to fall back to in the case that an entry in the mount table is not found. Consider the situation when you have a mount table that looks like:
> {code}
> /data -> hdfs://nn1/data
> /logs -> hdfs://nn1/logs
> /user -> hdfs://nn1/user
> /remote -> hdfs://nn2/remote
> {code}
> {{nn1}} here is being used as the primary, with a specific directory 'remote' being offloaded to another namenode. This works, but if we want to add another top-level directory to {{nn1}}, we have to update all of our client-side mount tables. Merge links (HADOOP-8298) could be used to achieve this but they do not seem to be coming soon; this special case of a default FS is much simpler - try to resolve through the VFS mount table, if not found, then resolve to the defaultFS.
> There is a good discussion of this at https://issues.apache.org/jira/browse/HADOOP-13055?focusedCommentId=15733822&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15733822



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