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https://issues.apache.org/jira/browse/HDFS-7146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14148243#comment-14148243
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Allen Wittenauer commented on HDFS-7146:
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nscd on the local host should prevent the load on the back-end server on a 
properly configured system.  (I recognize that a lot of people blankly disable 
all of nscd when all they really want is to disable hostname caches. This is 
still a misconfiguration.)

> NFS ID/Group lookup requires SSSD enumeration on the server
> -----------------------------------------------------------
>
>                 Key: HDFS-7146
>                 URL: https://issues.apache.org/jira/browse/HDFS-7146
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: nfs
>    Affects Versions: 2.6.0
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>
> The current implementation of the NFS UID and GID lookup works by running 
> 'getent passwd' with an assumption that it will return the entire list of 
> users available on the OS, local and remote (AD/etc.).
> This behaviour of the command is advised to be and is prevented by 
> administrators in most secure setups to avoid excessive load to the ADs 
> involved, as the # of users to be listed may be too large, and the repeated 
> requests of ALL users not present in the cache would be too much for the AD 
> infrastructure to bear.
> The NFS server should likely do lookups based on a specific UID request, via 
> 'getent passwd <UID>', if the UID does not match a cached value. This reduces 
> load on the LDAP backed infrastructure.
> Thanks [~qwertymaniac] for reporting the issue.



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