This paper deals with the design and dimensioning of a novel survivable optical network structure, called Petaweb, that can reach a total capacity of several Pb/s (10¹⁵ bit/s). The Petaweb has a composite-star architecture that allows two-hop connections between edge nodes through disconnected core nodes. Prior studies of the same authors have tackled the optimization of a Petaweb network architecture with regular and quasi-regular topologies. In this paper, reliability and survivability issues are addressed by introducing a dedicated path protection strategy into the design model. We present by extensive numerical results the reliability and survivability properties of the Petaweb core architecture with respect to single fiber link, core node, or switching plane failure and to switching site disconnection.