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LIS508 lecture 5: storage devices

LIS508 lecture 5: storage devices. Thomas Krichel 2002-10-21. Today we have fun with. Disks Files, directories and links. Files, directories and links. Files are continuous chunks data on disks that are required for software applications.

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LIS508 lecture 5: storage devices

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  1. LIS508 lecture 5: storage devices Thomas Krichel 2002-10-21

  2. Today we have fun with • Disks • Files, directories and links

  3. Files, directories and links • Files are continuous chunks data on disks that are required for software applications. • Directories are files that contain other files. Microsoft calls them folders. • A link is a file that contain the address of another file. Microsoft call it a shortcut.

  4. Structure of a disk • Disks are round devices divided into tracks and sectors. • A hard disk may have several physical disks. • Sector is 571 bytes long • 512 bytes are used by the user • The rest is reserved for disk operation • The disk spins, a head reads and writes data.

  5. Data integrity • The special data in each sector is kept there to try ensure that the user data is safe. • It contains a summary of the user data. • When the summary and the user data no longer match, the summary can be used to correct the user data. • SMART disks are those that can monitor if they are a in good shape.

  6. Formatting a floppy • Physical formatting: • writing tracks • writing sectors • Logical formatting: • labeling each sector • create boot record • create file allocation table (FAT)

  7. Formatting a hard disk • That is the same as formatting a floppy but • Between physical and logical formatting, the hard disk may be partitioned. • This allows for several logical disks on the same physical disk • Therefore the boot record is more complicated than on the floppy and called a master boot record MBR. • Example: dual boot Linux/Windows machine

  8. Windows logical disks • Floppies use FAT12 format • The boot records is exactly one sector long • therefore called the boot sector • Does not allow for long file names • The logical disks on a hard disks may use FAT32 format if larger than 512Mb • System area • Boot record • FAT • User area • Can handle disks of the size of 2 tera bytes

  9. NTFS • Is the file system for windows NT. • In windows XP, Microsoft have limited FAT32 to a capability to handle disks up to 8 Gb, to “encourage” the use of NTFS. • NTFS is a better file system • FAT is in the middle • Fragments less

  10. The root directory • Like a directory in the ground floor of a Manhattan building. • Root directory does not know where the file is stored, that is in the FAT. • Root directory is called drive:\ in windows, where drive is a letter identifying the drive. A drive is a physical device or a logical device found on a physical device. • The directory separator in Windows is “\”.

  11. Unix file conventions • In UNIX the root directory is “/”. • “/” is the directory separator. • A number of special files in “/dev” represent devices. • Each device is “mounted” as a subdirectory of the root directory. Example mount /dev/fd0 /floppy

  12. Long and short file names • DOS only had eleven byte file names, 8 for main name and three for the extension • Names could be uppercase letters, numerals, and some other symbols. • There is a generated short name that is used when windows writes to a disk that has a fat that does not support long names. • All modern Windows versions use unicode for file names.

  13. Folders in Windows • Rightclick, new allows you to create a new folder or shortcut • Within a folder you can have different views of the files • large icons (default) • list, column • Small icons, line) • Details, shows date, type

  14. copy • Either right-click and drag, select copy here • Or use right-click cut, and then you can paste it. • To delete, right-click and delete. • And then go to the recycling box and delete it from there. Otherwise no free space is created.

  15. Sort items • You can arrange icons by • Name • Type • Size • Date • You can set auto arrange on (see tick mark)

  16. Windows explorer • Shows directory tree and files in the current folder • Width of both parts can be customized • + next to a folder suggests that it contains further folders • Clicking on the plus can make the extra folders appear.

  17. Finding a file • Find / files or folders • Either name or substring • Date range • Type

  18. backups • There is a song of the Beatles… • The backup utility is based in the “system tools” section of programs/accessories. • It also has an emergency repair tool, that lets you fix things. • It is best to define a backup job, and then run it at scheduled times. • Time between jobs needs to be chosen with care.

  19. Next week • video

  20. http://openlib.org/home/krichel Thank you for your attention!

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