Storage

TechRepublic members know hard drives

More than 1,850 TechRepublic members demonstrated their knowledge of platters, tracks, and partitions in our Hard Drive Pop Quiz. Find out just how well they did and how well you would have done.


For this pop quiz, I decided to test our members' knowledge of a component no modern PC could do without, the hard drive. Over 1,850 TechRepublic members took the quiz and I'm glad to report that they nailed it, with no correct answers receiving less than 79 percent of the responses. Here's how the questions and answers broke down.

The disks within a hard disk

Figure A


The correct answer is: Platters, and 87 percent of the members who took the quiz got it right, as shown in Figure A. Hard drive platters are circular disks made from aluminum, glass, or ceramic. They have a thin magnetic coating on each side and are polished to a mirror-like smoothness (see Figure B). Each side of a platter is called a head.

Figure B
Hard drive platters are manufactured to very tight tolerances so that they can sustain the friction created when they spin below/above the read/write head at up to 3,000 inches per second (170 mph).


Several platters are then stacked together on a spindle. A space separates each platter and allows a read/write head to move above or below each head. As the platters spin together the read/write heads move to various points on each platter to access the requested data. Modern hard drives spin at either 5,400 or 7,200 revolutions per minute.

Cylinders, tracks, and sectors

Figure C


The correct answer to question two is: Tracks. As Figure C shows, 79 percent of those who took the quiz knew this answer. Unlike the platters mentioned above, logical cylinders aren't physical hard drive components, but a concept used to describe how data is stored on the drive.

Imagine each side of a platter is divided into sections like a pizza and also into concentric rings like the growth rings of a tree but of equal width. Each slice is called a sector and each ring is called a track. Each track is made up of a specific number of sectors. In older drives, both the inner tracks (nearest the platter's center) and the outer tracks (nearest the platter's edge) contained the same number of sectors. Modern drives however, use a technology called zone bit recording that allows the outer tracks to have more sectors than the inner tracks, thus increasing the amount of data the drive can store.

Now imagine an invisible cylinder, the width of a single track, passing vertically through the drive's stack of platters. This cylinder would pass through both the top and bottom of each platter, connecting a series of tracks. If a drive has three platters, our imaginary cylinder would connect six tracks, three top tracks and three bottom tracks. These six tracks make up a logical cylinder.

Seek time

Figure D


The correct answer is: The time it takes the actuator to move the read/write head to the selected track. Ninety-eight percent of our quiz takers knew this answer, as shown in Figure D. When the hard drive receives a request for data, it must position the read/write heads above or below the appropriate position on the head. This placement is accomplished by spinning the platters and moving the read/write heads. Many current EIDE hard drives have average seek times between 9 and 12 milliseconds, while SCSI drive seek times often range between 4 and 8 milliseconds.

Logical block addressing (LBA)

Figure E


The correct answer is: logical block addressing, as shown in Figure E, and 88 percent of those who took the quiz got this one right. LBA is a translation system that allows a computer's BIOS to address a hard disk larger than 528 MB. For more information on how LBA breaks the 528-MB barrier, check out this entry from CNET's Glossary of IT terms.

Partitioning

Figure F


After the 98 percent correct on question three, I didn't think the results would get any better, but the last question proved me wrong. A tremendous 99 percent of those who took the quiz knew the correct answer is: Partitioning, as shown in Figure F. A partition is a portion of a hard drive that acts as an independent unit. A single hard drive can be divided into several logical drives each with it's own volume name. This allows data to be organized more efficiently on the drive.

As for the other answers, files are stored in clusters on a hard drive, but clustering is actually a networking term used to describe the process of connecting several computers and making them function as a single machine. This is often done with network servers. Formatting a hard drive is the process of preparing a drive so the operating system can use it.

Defragmenting is the process of combining pieces of a file or sections of free space into a continuous unit. When a file is stored on a hard drive, there's no guarantee the entire file will be saved in the same place. The beginning of it may be saved on an outer track, while the end may be saved on an inner track. This can lengthen the time it takes a drive to retrieve a requested file. The more a file is opened, saved, edited, or copied the more fragmented it can be come. If a significant number of the files on a hard drive become fragmented, the PC will operate more slowly. To alleviate this problem, hard drives must be periodically defragmented. During the defragmentation process free space on the drive can also be consolidated.

Highest pop quiz scores to date
The scores posted on this hard drive quiz are by far the best pop quiz scores to date. To find out how TechRepublic members performed on previous pop quizzes check out these columns:

Send us your quiz topics
If you have a topic you'd like us to cover in an upcoming pop quiz, we want to hear about it. Drop us a line and share your suggestions for both quiz topics and questions. If you would like to comment about this quiz, please post a comment to this article. Good luck on our next quiz!

 

About Bill Detwiler

Bill Detwiler is Managing Editor of TechRepublic and Tech Pro Research and the host of Cracking Open, CNET and TechRepublic's popular online show. Prior to joining TechRepublic in 2000, Bill was an IT manager, database administrator, and desktop supp...

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