steveloughran opened a new pull request, #7281:
URL: https://github.com/apache/hadoop/pull/7281

   
   
   HADOOP-19229
   
   * default min/max are now 16K and 1M
   * s3a and abfs use 128K as the minimum size, 2M for max.
   
   Based on Facebook's velox paper's reported values: (20K for SSD, 500K  for 
cloud storage).
   
   Also adds new file `org.apache.hadoop.io.Sizes` which provides constants for
   various binary sizes, based on a file in hadoop-azure test source. This
   was NOT used anywhere else in the source other than in the new vector
   ranges -though it MAY/SHOULD be used in future.
   
   We should be aware that with a larger range, the possibility of failure of 
merged reads
   may increase, #71Ø5 HADOOP-19105. _Improve resilience in vector reads._ is 
intended to address this. This changes was on that commit chain, but has now 
been pulled out for independent review
   
   
   ### How was this patch tested?
   
   Existing tests rerun with assertions modified to cope with the changed 
defaults. Did find one unrelated regression in abfs test suites, filed as 
HADOOP-19382.
   
   No performance tests were done; any numbers here would be very insightful.
   
   
   ### For code changes:
   
   - [ ] Does the title or this PR starts with the corresponding JIRA issue id 
(e.g. 'HADOOP-17799. Your PR title ...')?
   - [ ] Object storage: have the integration tests been executed and the 
endpoint declared according to the connector-specific documentation?
   - [ ] If adding new dependencies to the code, are these dependencies 
licensed in a way that is compatible for inclusion under [ASF 
2.0](http://www.apache.org/legal/resolved.html#category-a)?
   - [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`, 
`NOTICE-binary` files?
   
   


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