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ADLS gen2 file listing performance tests

I was curious about which was the best approach for listing containers with many files and folders on an Azure Data Lake Storage - Gen2. In my experince, listing on ADLS-Gen2 is not so fast or, at least, it often does not fit my needs. So I wrote some code to try different approaches: classic listing - sync and async, and different level of parallelism. The keypoint is to find a good balance between parallelization, round-trip / overhead of HTTPS connections and numbers (--> cost) of API calls.

Results on my machine with my internet connection

  • client location: Italy
  • azure datacenter: West Europe (Nederland)
  • date: 2020-10-25
  • library: Azure.Storage.Files.DataLake 12.4.0
  • content: 112210 items
    • 1110 folders on 3 levels
      • folder1\folder2\folder3
    • 111100 files (100 files/folder)


Name Params Run1 Run2 Run3 API calls
ListSimple 36 31 33 23
ListAsync 38 30 34 23
PartiallyRecursive 0 30 31 29 31
PartiallyRecursive 1 8.5 9.2 9.0 111
PartiallyRecursive 2 7.8 9.0 8.9 1110
PartiallyRecursive >2 10.6 8.7 10.3 1110


Calling DataLake Storage API is quite expensive, in particular write operations.

The above tests costed me around € 2.38. As you can see in the table below, the main cost is related to creating files. For each file I have to create the file, append data and flush it.

API Calls Type Price Total €
CreatePathFile 113850 WriteOperation 0,00000592 0,6740
AppendFile 113850 WriteOperation 0,00000592 0,6740
FlushFile 113850 WriteOperation 0,00000592 0,6740
ListFilesystemDir 57650 IterativeRead 0,00000592 0,3413
CreatePathDir 3720 WriteOperation 0,00000592 0,0220
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