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What is the Directory Indexing Scanner and what does directory indexing accomplish?

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Applies to

  • Data ONTAP 9.2 and higher
  • Storage System Performance

Answer

As datasets have gotten larger and larger, performance can become a concern on those larger datasets. ONTAP has scaled to meet these needs as it has evolved, and one of those features is directory indexing.

  • Starting with ONTAP 9.2, a feature was introduced which will index directory sizes 2MB or larger .
  • Directory lookup will only read required blocks in the directory instead of entire directory.
  • Loading  100 directories of 10 MB each, prior to ONTAP 9.2, would require 1.25 GB of RAM.
  • Indexing the same 100 directories of 10 MB each in 9.2+ reduces this to around 200 MB of RAM.

This will be noticed in a few ways:

  • ONTAP upgrade. You will notice in "wafl scan status" a "directory index creation" scan.
  • Reboot may trigger a "directory index creation" scan as well.
  • A frontend call (lookup/create generally) will cause ONTAP to notice that the directory is greater than 2 MB and index it.
  • You may see in waffinity stats/wafl suspend data the WAFL messages related to indexing.

Additional Information

 

 

 

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