Drive PerformanceAverage access timeAlso known as seek timeTime to find desired dataMeasured in millisecondsDepends on two factorsRPMTime to access a trackHard drive between 6 and 12 msCD between 80 and 800 ms

Drive PerformanceData transfer rateHow fast data can be readMeasured in Bps or bpsHard drive ranges from 15 to 160 MBpsCD ROMS depend on X factor24x CD transfers 24 x 150 KBpsFloppy disks transfer at 45 KBps

Data Transfer Rate

Optimizing PerformanceDisk optimizationHandled by operating system toolRoutine disk maintenanceOptimization should be run monthly

Optimizing PerformanceClean up unnecessary filesDelete temp filesUninstall unused programsDelete obsolete data filesFiles should be cleaned weekly

Optimizing PerformanceScan a disk for errorsBad spots on the mediaFind and fix the errorMove data to a good spotMark the spot as badDisks should be scanned monthly

Optimizing PerformanceDefragment a diskFiles fragment when resavedFragmented files load slowerDefragment puts the fragments togetherDisks should be defragged monthly

Defragment

Optimizing PerformanceFile compressionShrinks the size of a fileTakes up less space on diskReduce a disks performanceWill increase disk capacityPKZip, WinZip and WinRAR

File Compression763 KB on diskCompressed157 KB

Drive Interface StandardsInterfaceHow the device is connectedDrive controllers allow transfer of dataDictates transfer rate and access time

Drive Interface StandardsEnhanced Integrated Drive ElectronicsEIDEGeneric term for drive controllersSeveral namesFast IDEAdvanced Technology Attachment (ATA)Up to 2 devices per controllerMost computers have 2 EIDE controllers

Drive Interface StandardsSmall Computer System InterfaceSCSIHigher transfer rates than EIDEMore than 40 devices per SCSI controllerComputers may have several SCSI controllersMany versions existVersions are typically incompatibleFound in servers and workstations

Drive Interface StandardsUSB and FireWireExternal drivesTransfer rate is limitedMany devices can be connected

Copyright 2006 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill Technology Education

Chapter 6BEnd of Chapter

Teaching tipTo provide contrast, present the speed of memory as measured in the nanoseconds, or billionth of a second. Then discuss virtual RAM as defined earlier in the text. More RAM, less virtual RAM makes a faster machine. Insider informationMost hard disks do not list the time to access a track. This is a good topic to tread lightly with. Teaching tipFigure 6B.3 on page 249 shows the disk cleanup utility for Windows XP. Insider informationWindows 9x required the screen saver to be disabled before running scan or defrag. Failing to disable the screen saver could lead to catastrophic data loss! Teaching tipMP3s are created using compression. If a audio song is recorded on a hard drive, the required storage is about 1 MB per second. When the MP3 compression is applied, the size is reduced to about 1 MB per minute.

Windows XP provides several compression routines. It provides for .zip file compression and archive creation. Zip archives can be accessed like normal folders. Folders can be compressed to shrink the contents. Finally, the entire disk can be compressed .Insider InformationSerial ATA (SATA) is a newer standard aimed at replacing EIDE/ATA. SATA is quite fast and easy to use. Teaching tipSCSI was introduced in chapter 5B of the text as a bus.