Performance Comparison of Prefetching and Placement Policies using Parallel I/O???
نویسندگان
چکیده
We present a simulation study of several prefetching policies to improve the I/O performance of external merging using parallel I/O. In particular we consider traditional sequential prefetch, forecast-based greedy prefetching, and oblivious prefetching. In conjunction with the prefetching policies we evaluate the bene t of two di erent data placement strategies: run-level striping and block-random placement, in the presence of data skew. We show that the I/O performance is greatly improved by using forecasting techniques. This method outperforms the other policies in achieving higher disk parallelism, and scales well with increased numbers of disks and increasing data skew. Additionally, the performance of block-random data placement is shown to be uniformly good, independent of the data skew, while the performance of run-level striped placement degrades with increasing skew.
منابع مشابه
Integrated Parallel Prefetching and Caching
Recently there has been a great deal of interest in prefetching from parallel disks, as a technique for enabling serial applications to improve I/O performance. Studies have also shown that for optimal performance, it is important to properly integrate prefetching and caching. In this paper, we study integrated prefetching and caching strategies for multiple disks. We present two algorithms, re...
متن کاملPractical Prefetching Techniques for Parallel File Systems
Improvements in the processing speed of multipro cessors are outpacing improvements in the speed of disk hardware Parallel disk I O subsystems have been proposed as one way to close the gap between proces sor and disk speeds In a previous paper we showed that prefetching and caching have the potential to de liver the performance bene ts of parallel le systems to parallel applications In this pa...
متن کاملA Trace-Driven Comparison of Algorithms for Parallel Prefetching and Caching (CMU-CS-96-174)
High-performance I/O systems depend on prefetching and caching in order to deliver good performance to applications. These two techniques have generally been considered in isolation, even though there are signi cant interactions between them; a block prefetched too early reduces the e ectiveness of the cache, while a block cached too long reduces the effectiveness of prefetching. In this paper ...
متن کاملA Cost-Bene t Scheme for High Performance Predictive Prefetching
High-performance computing systems will increasingly rely on prefetching data from disk to overcome long disk access times and maintain high utilization of parallel I/O systems. This paper evaluates a prefetching technique that chooses which blocks to prefetch based on their probability of access and decides whether to prefetch a particular block at a given time using a cost-beneet analysis. Th...
متن کاملRandomized Parallel Prefetching and Buffer Management
We show that deterministic algorithms using bounded lookahead cannot fully exploit the potential of a parallel I/O system. Randomization can be used to signi cantly improve the performance of parallel prefetching and bu er management algorithms. Using randomization in the data layout and a simple prefetching scheme, we show that a readonce reference string of length N can be serviced in (N=D) p...
متن کامل