This paper presents a new scheme based on the dynamical characteristics of P2P systems. First, the differences in node availability are taken into consideration, and a new data placement algorithm using less redundancy to guarantee target data availability is proposed. Second, permanent failure detector is used to distinguish between permanent and transient failures, which can reduce data recovery cost by decreasing the number of unnecessary repairs. Results from a trace-driven simulation suggest that this scheme can reduce about 80% maintenance bandwidth, compared with traditional methods.