1. A storage system, comprising: a first storage cluster, in a first chassis, the first storage cluster having a first plurality of storage nodes coupled together, each storage node of the first plurality of storage nodes having one or more storage units; a second storage cluster, in a second chassis, the second storage cluster having a second plurality of storage nodes coupled together, each storage node of the second plurality of storage nodes having one or more storage units; a chassis-to-chassis interconnect coupling the first storage cluster and the second storage cluster, with the first storage cluster and the second storage cluster configurable as a single logical unit; and the first storage cluster, the second storage cluster and the chassis-to-chassis interconnect having a pathway coupling storage units such that a first storage unit in the first storage cluster is configurable to communicate with at least one other storage unit in the first storage cluster and communicate with at least one storage unit in the second storage cluster, via the pathway without storage node processor assistance.