I know that EC2 is more flexible but more work over EMR. However in terms of costs, if using EC2 it probably requires EBS volumes attached to the EC2 instances, whereas AWS just streams in data from S3. So crunching the numbers on the AWS calculator, even though for EMR one must pay for EC2 also, EMR becomes cheaper than EC2 ?? Am i wrong here ?
Of course EC2 with EBS is probably faster, but is it worth the cost ?

thanks,
Matt

EMR does a lot of things for you that you won’t find on standard Hadoop on EC2. Some particularly important ones include

• Copying Hadoop logs from your machines to S3. This is very useful for debugging errors after the cluster has been shut down.
• Running job flows of multiple MapReduce, Pig, or Hive jobs
• Setting sensible configuration defaults based on hardware size you choose
• Access to spot instances for cheaper compute
• Ability to resize clusters dynamically

You’ll also find that the EMR S3 filesystem is faster and more reliable than the standard one packaged with Apache Hadoop. It supports Multipart upload, and streams writes directly to S3 rather than buffering to disk first. For a bit more on this, see Tip #5

Additionally, if you do decide to use EC2 directly, I’d recommend using instance-storage instead of EBS for your nodes. There’s really no reason to pay the extra cost of EBS for Hadoop; you’ll notice that EMR clusters all run on instance-storage nodes as well.