They still run HDFS, they just do it from S3. Presumably they are using EBS internally. This is exactly how you would do it if you set it up yourself... they'

They still run HDFS, they just do it from S3. Presumably they are using EBS internally. This is exactly how you would do it if you set it up yourself... they're just doing it for you. Small instances suck at Hadoop, you probably won't use them.