I am a consultant working on Hadoop installations across the globe. As an average I usually able to save 70% disk usage and 30% overall cost by changing the defaults to a reasonable value as well as migrating companies out of HDFS to something like S3. I have spent majority of my career (10 years) working on Hadoop and I can tell you that it is a terrible piece of software with insane ineffciency all over the place. If you would switch over all the Hadoop installations on Earth at once to something more reasonable it would be visible on the global CO2 production chart quite a bit. What is good for the bottom 90% of companies is a financial question not a technological question. It is a bit unfurtunate that Hadoop is so popular and nobody cares about efficiency, not even the Hadoop vendors (maybe with the exception of MapR, which is not opensource).