Parallel file systems deploy multiple metadata servers to distribute heavy metadata workload from clients. With the increasing number of metadata servers, metadata-intensive operations are facing some problems related with collaboration among them, compromising the performance gain. Consequently, a file system simulator is very helpful to try out some optimization ideas to solve these problems. In this paper, we propose DMFSsim to simulate the metadata-intensive operations on large-scale distributed metadata file systems. DMFSsim can flexibly replay traces of multiple metadata operations, support several commonly used metadata distribution algorithms, simulate file system tree hierarchy and underlying disk blocks management mechanism in real systems. Extensive simulations show that DMFSsim is capable of demonstrating the performance of metadata-intensive operations in distributed metadata file system.

In order to quickly determine the performance of a transient voltage suppressor (TVS), improve time domain identification capability of Elman network, the simulation of electromagnetic pulse (EMP) inject effects based on improved Elman network is proposed. Derivation proved that improved Elman network trained by standard BP algorithm has a similar form with the basic Elman network trained dynamic BP algorithm. We establish and improve its Elman network predictive modeling based on the measured parameters of TVS and then demonstrate that improved Elman network has the characteristics of quick speed, high precision, good performance and strong generalization ability, and broad use of prospects.