Organization of the file system
the directory is created with the relevant element with regard behalf compares
some file name (the file is not required to even exist at the time of the
creation of a symbolic connection). For symbolic link might create a separate
index node, and even scanned a single block of data to store potentially long
file name. Each of these methods has its downsides. In the case of rigid raises
the need to support the meter reference to a file for the correct implementation
of the operation delete a file. For example, in Unix, this count is one of the
attributes stored in the index node. Deleting a file a user reduces the number
of references to the file on 1. Actual removal of the file happens when the
number of references to the file becomes equal to 0. In the case of a symbolic
link such a problem does not arise since only the real owner is a link to the
index file node. If the owner removes the file, it is destroyed, and the
attempts of other users to work with him away in failure. Removing the symbolic
link has no effect on file. The problem of organizing a symbolic connection
velocity potential access to the file. The file contains a symbolic link path to
a file containing a list of nested directories for passing on which needed a few
hits to the disk. Symbolic Link has the advantage that it can be used to access
files uniformnogo remote computers, for example, if added to the road network
address of the remote machine. Cyclic Earl structure more flexible than a simple
tree, but work with it requires great accuracy. One of the major problems with
the structure of the cyclic column-assurance that the cycle does not arise in
finding a file. As of now, there are several ways to file, the program can
search to find his file on the disk several times. The simplest practical
solution to this problem is to limit the number of directories in the search.
Complete removal cycles rather laborious procedure performed by special
utilities and associated with multiple trace file system directories.
Cooperation processes when working with files. When different users work
together on a project, they often need to split the files. Shared file is shared
resource. As in the case of any shared resource, processes must synchronize
their access to shared files, directories, to avoid deadlocks, discrimination
individual processes and reduce system performance. For example, if several
users simultaneously editing a file and not taken special measures, the result
will be unpredictable and depends on the order in which records were implemented
in the file. Between the two operations read the same process, another process
can modify data, which is unacceptable for many applications. The simplest
solution to this problem be allowed to seize one of the file that is blocking
access to shared file other
Next part
|
O
wlCom Software
