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Inode Cache - file operations suspend heavily creating massive latency

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Category:
ontap-9
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perf
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Applies to

  • ONTAP 9
  • NFS
  • SMB

Issue

Overall very poor performance for file/directory based operations, with the following possible symptoms:

  • Many long running READDIR/READDIR+ requests could be identified from a packet trace, it could take up to tens of seconds, or even hundreds of seconds in the worst case scenario 
    • Note:  The same applies to SMB2 QUERY_DIRECTORY requests or its equivalents in other SMB versions
  • High latency for other file operation types, such as GETATTR, LOOKUP, ACCESS, etc. 
  • Timeout on the NFS/SMB clients
  • Extremely high latency reported from various Performance Monitoring tools
  • The following wafl.readdir.expired error message from EMS could indicate the presence of a similar issue

[<node_name>: wafl_exemptxx: wafl.readdir.expired:error]: A READDIR file operation has expired for the directory associated with volume <volume_name>/@vserver:<vserver_uuid> Snapshot copy ID xx and inode <inode_number>.


 

 

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