@Article{barve:mergesort, author = {Rakesh D. Barve and Edward F. Grove and Jeffrey S. Vitter}, title = {Simple Randomized Mergesort on Parallel Disks}, journal = {Parallel Computing}, year = {1997}, volume = {23}, number = {4}, publisher = {North-Holland (Elsevier Scientific)}, note = {To appear}, keyword = {verify, parallel I/O algorithm, sorting, pario-bib}, abstract = {We consider the problem of sorting a file of N records on the D-disk model of parallel I/O in which there are two sources of parallelism. Records are transferred to and from disk concurrently in blocks of B contiguous records. In each I/O operation, up to one block can be transferred to or from each of the D disks in parallel. We propose a simple, efficient, randomized mergesort algorithm called SRM that uses a forecast-and-flush approach to overcome the inherent difficulties of simple merging on parallel disks. SRM exhibits a limited use of randomization and also has a useful deterministic version. Generalizing the technique of forecasting, our algorithm is able to read in, at any time, the ``right'' block from any disk, and using the technique of flushing, our algorithm evicts, without any I/O overhead, just the ``right'' blocks from memory to make space for new ones to be read in. The disk layout of SRM is such that it enjoys perfect write parallelism, avoiding fundamental inefficiencies of previous mergesort algorithms. By analysis of generalized maximum occupancy problems we are able to derive an analytical upper bound on SRM's expected overhead valid for arbitrary inputs. \par The upper bound derived on expected I/O performance of SRM indicates that SRM is provably better than disk-striped mergesort (DSM) for realistic parameter values D, M, and B. Average-case simulations show further improvement on the analytical upper bound. Unlike previously proposed optimal sorting algorithms, SRM outperforms DSM even when the number D of parallel disks is small.} } @InProceedings{chang:titan, author = {Chialin Chang and Bongki Moon and Anurag Acharya and Carter Shock and Alan Sussman and Joel Saltz}, title = {{Titan}: a High-Performance Remote-sensing Database}, booktitle = {Proceedings of the Thirteenth International Conference on Data Engineering}, year = {1997}, month = {April}, address = {College Park, MD}, URL = {ftp://hpsl.cs.umd.edu/pub/papers/icde97.ps.Z}, abstract = {There are two major challenges for a high-performance remote-sensing database. First, it must provide low-latency retrieval of very large volumes of spatio-temporal data. This requires effective declustering and placement of a multi-dimensional dataset onto a large disk farm. Second, the order of magnitude reduction in data-size due to post-processing makes it imperative, from a performance perspective, that the postprocessing be done on the machine that holds the data. This requires careful coordination of computation and data retrieval. This paper describes the design, implementation and evaluation of {\em Titan}, a parallel shared-nothing database designed for handling remote-sensing data. The computational platform for Titan is a 16-processor IBM SP-2 with four fast disks attached to each processor. Titan is currently operational and contains about 24~GB of AVHRR data from the NOAA-7 satellite. The experimental results show that Titan provides good performance for global queries and interactive response times for local queries.} } @TechReport{cormen:early-vic-tr, author = {Thomas H. Cormen and Melissa Hirschl}, title = {Early Experiences in Evaluating the Parallel Disk Model with the {ViC*} Implementation}, year = {1996}, month = {August}, number = {PCS-TR96-293}, institution = {Dept. of Computer Science, Dartmouth College}, later = {cormen:early-vic}, URL = {http://www.cs.dartmouth.edu/reports/abstracts/TR96-293/}, keyword = {parallel I/O, parallel I/O algorithm, compiler, pario-bib}, abstract = {Although several algorithms have been developed for the Parallel Disk Model (PDM), few have been implemented. Consequently, little has been known about the accuracy of the PDM in measuring I/O time and total time to perform an out-of-core computation. This paper analyzes timing results on a uniprocessor with several disks for two PDM algorithms, out-of-core radix sort and BMMC permutations, to determine the strengths and weaknesses of the PDM. \par The results indicate the following. First, good PDM algorithms are usually not I/O bound. Second, of the four PDM parameters, two (problem size and memory size) are good indicators of I/O time and running time, but the other two (block size and number of disks) are not. Third, because PDM algorithms tend not to be I/O bound, asynchronous I/O effectively hides I/O times. \par The software interface to the PDM is part of the ViC* run-time library. The interface is a set of wrappers that are designed to be both efficient and portable across several parallel file systems and target machines.}, comment = {This used to be called cormen:early-vic but I renamed it because the paper will appear in parcomp.} } @Article{moon:declustering, author = {Bongki Moon and Joel H. Saltz}, title = {Scalability Analysis of Declustering Methods for for Multidimensional Range Queries}, year = {1997}, note = {To appear}, URL = {ftp://hpsl.cs.umd.edu/pub/papers/ieee_tkde.ps.Z}, abstract = {Efficient storage and retrieval of multi-attribute datasets have become one of the essential requirements for many data-intensive applications. The Cartesian product file has been known as an effective multi-attribute file structure for partial-match and best-match queries. Several heuristic methods have been developed to decluster Cartesian product files across multiple disks to obtain high performance for disk accesses. Though the scalability of the declustering methods becomes increasingly important for systems equipped with a large number of disks, no analytic studies have been done so far. In this paper we derive formulas describing the scalability of two popular declustering methods Disk Modulo and Fieldwise Xor for range queries, which are the most common type of queries. These formulas disclose the limited scalability of the declustering methods and are corroborated by extensive simulation experiments. From the practical point of view, the formulas given in this paper provide a simple measure which can be used to predict the response time of a given range query and to guide the selection of a declustering method under various conditions.} } @Article{parsons:templates, author = {Ian Parsons and Ron Unrau and Jonathan Schaeffer and Duane Szafron}, title = {{PI/OT}: Parallel {I/O} Templates}, journal = {Parallel Computing}, year = {1997}, volume = {23}, number = {4}, publisher = {North-Holland (Elsevier Scientific)}, note = {To appear}, keyword = {verify, parallel I/O, pario-bib}, abstract = {This paper presents a novel, top-down, high-level approach to parallelizing file I/O. Each parallel file descriptor is annotated with a high-level specification, or template, of the expected parallel behaviour. The annotations are external to and independent of the source code. At run-time, all I/O using a parallel file descriptor adheres to the semantics of the selected template. By separating the parallel I/O specifications from the code, a user can quickly change the I/O behaviour without rewriting code. Templates can be composed hierarchically to construct complex access patterns.} } @Article{schwabe:jlayouts, author = {Eric J. Schwabe and Ian M. Sutherland}, title = {Evaluating Approximately Balanced Parity-Declustered Data Layouts for Disk Arrays}, journal = {Parallel Computing}, year = {1997}, volume = {23}, number = {4}, publisher = {North-Holland (Elsevier Scientific)}, note = {To appear}, earlier = {schwabe:layouts}, keyword = {verify, disk array, parity, RAID, parallel I/O, pario-bib}, abstract = {Parity-declustered data layouts were developed to reduce the time for on-line failure recovery in disk arrays. They generally require perfect balancing of reconstruction workload among the disks; this restrictive balance condition makes such data layouts difficult to construct. In this paper, we consider approximately balanced data layouts, where some variation in the reconstruction workload over the disks is permitted. Such layouts are considerably easier to construct than perfectly balanced layouts. We consider three methods for constructing approximately balanced data layouts, and analyze their performance both theoretically and experimentally. We conclude that on uniform workloads, approximately balanced layouts have performance nearly identical to that of perfectly balanced layouts.} }