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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.

This paper is dedicated to investigating an observer-based fault diagnosis (FD) approach for a Lipschitz nonlinear system and applied in a stratospheric airship (SA) flight control system. The system model uncertainties, external disturbances, and sensor noise are considered. Firstly, a detailed model of the SA is obtained by kinematics and dynamics. Then a nonlinear fault detection observer is designed via Linear Matrix Inequation (LMI) in H∞ framework, and a bank of unknown input observers is activated for isolating the faulty component. Moreover, to estimate the size of the fault, an expanded robust estimation observer is designed concerning states and fault estimator error. All of the mentioned observers are designed by a matrix inequation formulation, which reformulated the nonlinear system to a generalized Linear Parameter Varying (LPV) system mathematically. The proposed FD scheme is applied to the control system of a SA and its effectiveness is illustrated. Mathematics Subject Classification (2020) MSC code1 · MSC code2 · more