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

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.
• A 10MB directory file prior to ONTAP 9.2 would require 1.25 GB of RAM.
• Indexing this same file in 9.2+ reduced 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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