Testbed guideline

I'm in the process of building a small testbed to test performance of
ES. Would you have any hardware recommendation? I'm looking to build a
2 node cluster initially and scaling it until I reach say 5 nodes. I
want to evaluate performance and key features such as high-
availability/redundancy.

What is most important in selecting the hardware? For example, should
I get fast disk such as 15KRPM SAS, but low capacity or high capacity
7200RPM SATA drives? How many core make sense? How much memory? Any
insight is greatly appreciated. Specific recommendation such as Dell
R410, 415, welcome.

JF.