Organization of the file system
modern OS file systems contain special funds to support their own compatibility.
The integrity of the file system. An important aspect of reliable file system
control its integrity. As a result, disk blocks File operations can read into
memory, modified, and then written to disk. And, many file operations involve
multiple file system objects. And if, because of the unpredictable stop system
on the disk changes will be saved only for a part of these objects (broken
atomarnost file operations), the file system on the disk may be left in a
position inconsistent. As a result of a breach of logic may work with the data,
for example, appear lost disk blocks, which do not belong to any file, while
labeled employed, or vice versa blocks marked as free, but at the same time
employed (on them there is a reference in the index node), or other violations.
In modern OS includes measures to minimize the damage from the damage of the
file system and then restore its integrity. Obviously, the correct functioning
of the file system, the significance of individual data mixed. The distortion of
the contents of user files do not result in serious (in terms of file system)
effects, while inconsistencies in the files containing information Manager (directory,
index nodes, superblock, etc.) can be catastrophic. Therefore, should be
carefully thought out manner with the commission of the transaction file system
data structures. That's an example of the creation of a rigid connection to a
file. To do so, the file system must do the following operations: 1. Create a
new entry in the directory node pointing to the index file 2. Enlarge meter ties
in a knot index If an emergency shutdown occurred between 1-st and 2-nd
operations, the file system directories will be two filename, addressable node
with the value of the index meter connections equal to 1. if now will remove one
of the names, it will delete the file itself. If the same procedures and
operations changed, as before, the stop occurred between the first and second
operations, the file will be nonexistent tight relationship, but the existing
entry in the directory will be correct. While this is a mistake, too, but its
effects less serious than in the previous case. Another means of support for the
integrity of the file is the way to realize peace in the form of the transaction,
as some, as is the DBMS. Follow with objects during operations recorded file,
and if there shutdown system, with a protocol in place, you can implement a
system rollback ago in the original holistic state in which it remained until
the start of the operation. Such logging implemented in NTFS. If the violation
still occurred, in order to eliminate the problem of incompatibility can resort
to the utility (fsck, chkdsk, scandisk and others), who check
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