LIS508 lecture 5: storage devices Thomas Krichel

Today we have fun with Disks 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.

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.

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.

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

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

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

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

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 “\”.

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

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.

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

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.

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

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.

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

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.

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Thank you for your attention!