Separate Configurations for Head and Worker Nodes

[PiercingDan]

It would be good to have separate configurations for head and worker nodes, for example, separate instance types, AMIs, and EBS volume sizes for head and worker nodes.

EDIT: I see a pull request is currently underway for separate master/worker instance types. Perhaps separate AMIs and EBS volume sizes would also be doable.

[nchammas]

Related: #166, #241.

[pferrel]

+1

You can't create just a master with slaves = 0. Otherwise you could create the master with one instance type then add-slaves with another.

[devyn]

I would really like this because small clusters don't need a ton of compute resources for the master. You could drive 4 slaves of a relatively large instance type with a master of a much smaller instance type depending on your application and be totally fine.

Edit: it also seems like it would be quite easy to implement compared to colocating one slave on the same machine as the master, which should probably be optional because I would imagine that in clusters with hundreds of slaves, the master does need to have some beef to it.