S3 Performance Checklist

There are various types of checklists that you can use to ensure optimal performance when working with data in S3.

Checklist for Data

[ ] Amazon S3 bucket is in same region as the EC2-hosted cluster.
[ ] The directory layout is "shallow". For directory listing performance, the directory layout prefers "shallow" directory trees with many files over deep directory trees with only a few files per directory.
[ ] The "pseudo" block size set in fs.s3a.block.size is appropriate for the work to be performed on the data.
[ ] Copy to HDFS any data that needs to be repeatedly read to HDFS.

Checklist for Cluster Configurations

[ ] Set yarn.scheduler.capacity.node-locality-delay to 0 to improve container launch times.

Checklist for Code

[ ] Application does not make rename() calls. Where it does, it does not assume the operation is immediate.
[ ] Application does not assume that delete() is near-instantaneous.
[ ] Application uses FileSystem.listFiles(path, recursive=true) to list a directory tree.
[ ] Application prefers forward seeks through files, rather than full random IO.
[ ] If making "random" IO through seek() and read() sequences or and Hadoop's PositionedReadable API, fs.s3a.experimental.input.fadvise is set to random.

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