title: How to diff very large buckets in Amazon S3?
body: <p>I have a use case where I have to back up a 200+TB, 18M object S3 bucket to another account that changes often (used in batch processing of critical data). I need to add a verification step, but due to the large size of both bucket, object count, and frequency of change this is tricky. </p>
  
  <p>My current thoughts are to pull the eTags from the original bucket and archive bucket, and the write a streaming diff tool to compare the values. Has anyone here had to approach this problem and if so did you come up with a better answer?</p>