I have done a lot of reading about rpi clusters. Don't worry I am not going to ask if they function as a single virtual computer. I understand that they can be used to divide up complex tasks or space out tasks in parallel programming. Basically I want to create a home automation system, weather station, and add on a couple other projects I may find cool in the future. I just want to know if I can outfit each rpi in the cluster to do a specific one of these functions. They all require different peripherals attached to each rpi and I am not sure how much control over these peripherals I will have from the head node. Any clarification would be appreciated. Thanks.
Depending on how you build your cluster, you can
ssh individually to each of the nodes from the head node, or even
ssh directly from your PC into each node.
In short, your cluster can still act like individual Pis. They can still do individual jobs. Do whatever you want with them.
The cluster-ness will only kick in when you need it (e.g. when you run a cluster-based distributed calculation thing, or when you fold proteins). Otherwise, they will simply act as a networked group of Pis. Depending on how you build your cluster