vinaysbadami commented on pull request #2795:
URL: https://github.com/apache/hadoop/pull/2795#issuecomment-842000750


   @anoopsjohn  ==> wrt your comment on "will this hamper spark jobs".
   1. This is a speculative read ahead. So whenever this is wrong, it is waste 
io and iops.
   2. With parquet etc, the reads tend to be random. Hence a smaller read ahead 
depth is prefereable
   3. Based on debugging various customer perf isues, we rarely saw benefit of 
> 2
   4. This config is per inputstream and not global across streams.
   


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