Kallahalla, MaheshVarman, Peter J.2015-09-152015-09-152002-11M. Kallahalla and P. J. Varman, "PC-OPT: Optimal Offline Prefetching and Caching for Parallel I/O Systems," <i>IEEE Transactions on Computers,</i> vol. 51, no. 11, 2002.https://hdl.handle.net/1911/81639Abstract—We address the problem of prefetching and caching in a parallel I/O system and present a new algorithm for parallel disk scheduling. Traditional buffer management algorithms that minimize the number of block misses are substantially suboptimal in a parallel I/O system where multiple I/Os can proceed simultaneously. We show that in the offline case, where a priori knowledge of all the requests is available, PC-OPT performs the minimum number of I/Os to service the given I/O requests. This is the first parallel I/O scheduling algorithm that is provably offline optimal in the parallel disk model. In the online case, we study the context of global L-block lookahead, which gives the buffer management algorithm a lookahead consisting of L distinct requests. We show that the competitive ratio of PC-OPT, with global L-block lookahead, is M ÿ L D , when L M, and MD=L , when L > M, where the number of disks is D and buffer size is M.engJournal articleI/OInformation StorageElectrical and Computer EngineeringParallel I/O Systemscachingprefetchingschedulingbuffer managementcompetitive ratioalgorithmsonline algorithmoffline algorithmhttp://dx.doi.org/10.1109/TC.2002.1047757