Data Structures and Algorithm Analysis - Computer Science at ...

Sec. 8.6 Further Reading 295• Use as much working memory as possible. Applying more memory usuallyspeeds processing. In fact, more memory will have a greater effect than afaster disk. A faster CPU is unlikely to yield much improvement in runningtime for external sorting, because disk I/O speed is the limiting factor.• If possible, use additional disk drives for more overlapping of processingwith I/O, and to allow for sequential file processing.8.6 Further ReadingA good general text on file processing is Folk and Zoellick’s File Structures: AConceptual Toolkit [FZ98]. A somewhat more advanced discussion on key issues infile processing is Betty Salzberg’s File Structures: An Analytical Approach [Sal88].A great discussion on external sorting methods can be found in Salzberg’s book.The presentation in this chapter is similar in spirit to Salzberg’s.For details on disk drive modeling and measurement, see the article by Ruemmlerand Wilkes, “An Introduction to Disk Drive Modeling” [RW94]. See AndrewS. Tanenbaum’s Structured Computer Organization [Tan06] for an introduction tocomputer hardware and organization. An excellent, detailed description of memoryand hard disk drives can be found online at “The PC Guide,” by Charles M.Kozierok [Koz05] (www.pcguide.com). The PC Guide also gives detailed descriptionsof the Microsoft Windows and UNIX (Linux) file systems.See “Outperforming LRU with an Adaptive Replacement Cache Algorithm”by Megiddo and Modha [MM04] for an example of a more sophisticated algorithmthan LRU for managing buffer pools.The snowplow argument comes from Donald E. Knuth’s Sorting and Searching[Knu98], which also contains a wide variety of external sorting algorithms.8.7 Exercises8.1 Computer memory and storage prices change rapidly. Find out what thecurrent prices are for the media listed in Figure 8.1. Does your informationchange any of the basic conclusions regarding disk processing?8.2 Assume a disk drive from the late 1990s is configured as follows. The totalstorage is approximately 675MB divided among 15 surfaces. Each surfacehas 612 tracks; there are 144 sectors/track, 512 bytes/sector, and 8 sectors/cluster.The disk turns at 3600 rpm. The track-to-track seek time is20 ms, and the average seek time is 80 ms. Now assume that there is a360KB file on the disk. On average, how long does it take to read all of thedata in the file? Assume that the first track of the file is randomly placed onthe disk, that the entire file lies on adjacent tracks, and that the file completelyfills each track on which it is found. A seek must be performed each time theI/O head moves to a new track. Show your calculations.