File Systems Explained

List a directory. In order to use the disk properly the user will require to know whats in all the diretories stored on it. On top of this the user needs to be able to browse through the directories on the hard drive.

Since the first directory structures were designed they have gone through several large evolutions. Before directory structures were applied to file systems all files were stored on the same level. This is basically a system with one directory in which all the files are kept. The next advancement on this which would be considered the first directory structure is the two level directory. In this There is a singe list of directories which are all on the same level. The files are then stored in these directories. This allows different users and applications to store there files separately. After this came the first directory structures as we know them today, directory trees. Tree structure directories improves on two level directories by allowing directories as well as files to be stored in directories. All modern file systems use tree structore directories, but many have additional features such as security built on top of them.

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Protection can be implemented in many ways. Some file systems allow you to have password protected directories. In this system. The file system wont allow you to access a directory before it is given a username and password for it. Others extend this system by given different users or groups access permissions. The operating system requires the user to log in before using the computer and then restrict their access to areas they dont have permission for. The system used by the computer science department for storage space and coursework submission on raptor is a good example of this. In a file system like NTFS all type of storage space, network access and use of device such as printers can be controlled in this way. Other types of access control can also be implemented outside of the file system. For example applications such as win zip allow you to password protect files.

There are many different file systems currently available to us on many different platforms and depending on the type of application and size of drive different situations suit different file system. If you were to design a file system for a tape backup system then a sequential access method would be better suited than a direct access method given the constraints of the hardware. Also if you had a small hard drive on a home computer then there would be no real advantage of using a more complex file system with features such as protection as it isn’t likely to be needed. If i were to design a file system for a 10 gigabyte drive i would use linked allocation over contigious to make the most efficient use the drive space and limit the time needed to maintain the drive.

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I would also design a direct access method over a sequential access one to make the most use of the strengths of the hardware. The directory structure would be tree based to allow better organisation of information on the drive and would allow for acyclic directories to make it easier for several users to work on the same project. It would also have a file protection system that allowed for different access rights for different groups of users and password protection on directories and individual files.Several file systems that already implement the features ive decribed above as ideal for a 10gig hard drive are currently available, these include NTFS for the Windows NT and XP operating systems and ext2 which is used in Linux.