um, you sound like a vendor. hadoop does mean map-reduce + hdfs as the common usage by the majority of devs + admins. Claiming hadoop is now some distribution o

um, you sound like a vendor. hadoop does mean map-reduce + hdfs as the common usage by the majority of devs + admins. Claiming hadoop is now some distribution of tools is fine, but that's simply not what the common usage is. I am a Hadoop developer, and I can tell you that Hadoop does not mean "map-reduce + hdfs". That's also not what people are installing when they install Cloudera's distribution of Hadoop, Hortonworks' distribution of Hadoop, or even Intel's distribution of Hadoop (which is being discontinued in favor of adopting Cloudera's). This is more old information from 2008, being replayed as current. YARN even lives in the Hadoop source code repository, it's hard to get more "Hadoop" than that. Spark has its own repo, but it uses many classes from Hadoop like InputFormat, etc. It remains to be seen if yarn will carry the day or no; my suspicion is that many people are essentially going to be running spark on hdfs. I don't see much use for yarn unless you need to balance hadoop and yarn, and weren't their claims that yarn was going to support eg mpi style computation that didn't pan out? Much confusion. Much sadness. You run YARN (or its close competitor, Mesos) because you want to have multiple jobs going on in the same cluster at once. You need things like per-user queues, job control, reserving CPU and memory resources. The jobs going on at once may be multiple MapReduce jobs, or they may be multiple Spark jobs. Even Databricks, which employs many of the early Spark developers, doesn't ship a product that runs Spark in standalone mode. They run on Mesos.