In this paper we present a Robust data Replication Algorithm (RRA) for MANETs. RRA ensures persistent data availability by duplicating data over replicanodes, while minimizing the consumption of radio resources. RRA is the first algorithm thoroughly designed to operate in environments with node failures and radio obstacles (e.g., buildings, walls). Our challenge is to consider such impairments as "accidental"; i.e., their occurrence neither can be run-time predicted, nor can be a-priori quantified in terms of probability. As instance, this is the case of nodes wandering in an unknown territory. To cope efficiently with the novel challenge, we suggest a practical assumption: during a refresh period, only a single accidental impairment may occur. Following this assumption, we succeed in formalizing (and solving) the resource minimization problem as the finding of a minimum-cost-set-cover. We assess RRA performance through NS2 simulations. Simulation code is released as open-source. ©2010 IEEE.