When setting up Hadoop, whirr.hardware-id is used in the configuration to set a single instance size/type for both nn,jt and dn,tt roles, but there are workloads that benefit from having a different instance size/type for each role. This need is even greater for ensembles with Zookeeper and HBase.
Without this, a small Whirr cluster underutilizes resources.
whirr.hardware-id should be a used to set a default instance size/type, and variations like whirr.$
.hardware-id could be used to set size/type more specifically. This is a simple, obvious, and easy to implement mechanism to provide this functionality.