EMC Isilon is a scale out NAS solution that can grow from 3 to 144 nodes and up to 20PB in a single File-system. In my experience it is also the easiest platform to install, and configure, and customers tell me on a regular basis they feel the same way about the day to day operations. It already expands on the fly when a new node is added the system. The system will automatically recognize the node in the cluster, assign it an IP address, rebalance the data in the background, and capacity is immediately available. System cache is globally shared, and protection overhead decreases as the cluster grows. This all means that the more you grow the cluster, the faster and more efficient it becomes. All in all Isilon was already an impressive soluition and yet it is going to get even better.