CH05_b_StorageDriveMaintenance

CH05_b_StorageDriveMaintenance - Storage Drive Maintenance...

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Storage Drive Maintenance 5b-1 Chapter 5b: Storage Management and Maintenance Knowing a bit about storage and the practical aspects of using and maintaining disks has given me one of the most rewarding experiences in my career as a teacher. Janis, one the students who took my course some years ago, had been doing an internship for which she had to keep a detailed diary of her rich experiences. One afternoon near the end of the quarter, she called me almost in tears. She had kept her diary in a floppy disk that she carried around so she could work at the computer labs. Somehow, her file had disappeared from the disk. She remembered what she had learned about file recovery and called me. “Do not put the disk into any computer and come right over,” I said. “I remember what you told us,” she replied. “I have not touched it since the file disappeared.” She explained that the files represented several weeks of work, and she had no other copy, not even hard copy. When Janis arrived in my office I saw she had been crying. Although I was careful not to lead her to premature hope before I could look at the disk, she seemed relieved that I would try to help her. After I did some work on the disk with demo software 1 that I downloaded from the web, I asked her to take a look at the screen to let me know if it looked familiar. Not knowing anything about the files she was missing, the text on the screen had the same emotional impact on me as a page of a cookbook. Definitely not so for Janis. She took over the computer and scrolled up and down the text. “That’s pretty much the whole thing!” She looked at me with a big smile. Recollection and understanding of the following information helped Janis avert a catastrophe. T YPES OF F ILES To read and write data "permanently," disk drives encode the surfaces of disks with individual bits that represent characters (letters and symbols). Each bit is represented by the polarity of the tiny magnetic fields created on the surface of the platters. North up is a one and north down is a zero. There are various types of files, such as program files (which contain software), data files, and graphics files (which contain digital encoding of images). File names are used to specify which file to use; different systems limit the length of file names and some use extensions to indicate the file type. Thus, .xlsx indicates the file is an MS Excel document, .docx indicates a MS Word document, and so on. F ORMATTING D ISKS Before a magnetic disk can be used for storage, it must be formatted. Formatting prepares the physical medium for storage, and creates logical structure on the disk. 1 I used R-Studio from http://www.r-studio.com/.
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Storage Drive Maintenance 5b-2 There are two types of formatting: low-level or full format , and quick format . The first time a disk is formatted always requires a full format. During this procedure, the disk heads create magnetic marks that organize each disk surface into tracks and sectors. Tracks are
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CH05_b_StorageDriveMaintenance - Storage Drive Maintenance...

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