Small and medium-sized companies encounter enormous difficulties when trying to implement lean production methods according to the role model of the Toyota Production System. This is caused by the varying effects of lean methods on production figures depending on the production conditions concerning product variety and volumes, variation of process and set-up times, etc. This article presents approaches developed at the Institute of Production Science (wbk), Karlsruhe Institute of Technology, to evaluate and optimize the effects of lean methods in small series productions based on the quantified interdependencies with the relevant target figures. It enables the best combination of lean methods to be identified and recommendations for the efficient implementation of these lean methods.
One challenge in applying erasure codes (or error-correcting codes) to distributed storage systems is to maintain consistency between data and redundancy blocks in the face of crashing servers. We present two access protocols that provide sequential consistency and maximum distance separable fault tolerance at the same time. The protocols use sequence numbers to recover a consistent version in the presence of failures or partial writes. The first (pessimistic) PSW protocol uses a master per stripe to execute updates in sequence. The second (optimistic) OCW protocol allows concurrent writes to blocks in the same stripe to happen in parallel at the cost of additional buffer space.We present empirical performance results for PSW and OCW and compare them to other protocols. Our results show that OCW is as fast as simple replication while providing better fault tolerance and/or reduced storage overhead. This demonstrates that erasure coding can be used as a space-efficient alternative to replication in distributed storage systems.
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