True but Hadoop is the whole tooling and with YARN they are distancing themselves from Map/Reduce. IMHO, it looks like they are heading in that right direction but not quite there. That why it maybe v4 before we can think of Hadoop as an OS for datacenter.

Mesos is closer to the metal but still is only a piece of what is needed. Picturing it as an OS is misleading while picturing Hadoop V2 as a proto-OS is not that much in accurate.