Racking and clustering Raspberries is still mostly a game – http://www.jeffgeerling.com/blog/ansible-deployments-visualized-raspberry-pi – with education being an exception. However, Raspberry Pi Zero permits to solve certain tasks differently – I got some inspiration from – http://hackaday.com/2016/01/25/raspberry-pi-zero-cluster-packs-a-punch/ . The new keyword is compartmentalization.
It is now possible to create robust and “compartmentalized” solutions. The first RasPi could handle the communications (VPN calls to home) and rsyncs, the second one will host a myriad of sensors (gyro, GPS, acceleration) while the third one could meanwhile play mp3s or videos. It is yet possible to add the fourth one (this time not Zero) keeping 60 secs worth of video of already passed time. Did you recognize your new car computer?
Below is a poor man PoC about it, how one should/could/might rack Pi Zeros for a compartmentalized solution.