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Consider this procedure in the case file / bin / my_shell / print belonging to
the file system shown in Fig. 7.17. Determining the physical address of the file
consists of the following steps. 1. First seen root to find the first part of
the symbolic name-bin. Determine the number (in this example 6) index descriptor
directory, which is in the root. Address root known to the system. 2. Out of
descriptors read descriptor index number 6. Start address descriptor is
determined by the number of known system of primary sector index descriptors and
descriptor size of the index. Of the index descriptor 6 is a physical address of
/ bin. 3. You are currently viewing / bin to find the second part of the
symbolic name my_shell. Determine the number descriptor index of / bin /
my_shell (in this case, 25). 4. Read index descriptor 25, is a physical address
/ bin / my_shell. 5. You are currently viewing / bin / my_shell be determined
number index file descriptor print (in this case, 131). 6. Of the 131 identified
descriptor index number blocks, as well as other characteristics of the / bin /
my_shell / print. This procedure requires, in general, several appeals to the
disk, with the number of full filename. To reduce the average time access to his
file descriptor copied in a special system area of RAM. Copying descriptor index
is a procedure to open it. The physical organization of ufs file system differs
from the physical organization described file system s5 that section consists of
a repeated sequence of several "zagruzchik- superblok- block group tsilindrov-
area index descriptors" (Figure 7.18).
In these repetitive sequences of super is the main backup copies of the first
super. When damage to the main super copies can be used backup super. Areas of
the same group cylinder block and index descriptors provide individual values
for each sequence. Bloc Party describes the number of cylinders index
descriptors and blocks located on the group cylinder drive. This group is to
speed up access to view the index data descriptors and files described these
descriptors, or result in too much head movement disk. In addition, ufs file
names can be up to 255 characters long (ASCII encoding, one byte at symbol),
while s5 length of the name can not exceed 14 characters.
The physical organization of NTFS NTFS file system was designed as a basic file
system for Windows NT in the early 90 years based on the experience of FAT file
systems and HPFS (the main file system for OS / 2), as well as other existing at
the time of file systems. The main distinguishing characteristic of NTFS are:
Support large files and large disk up to 2 bytes; vosstanavlivaemost after
faults and failures of programmes and equipment management discs; A high speed
operations, including the large disk; Low fragmentation, including the large
disk; flexible structure which allows the development by adding new types of
entries and attributes of files preserving compatibility with previous versions
of FS; resistance to bounce disk drives; Support long character names;
Controlling access to folders and individual files.
The structure that NTFS Unlike FAT partitions and s5/ufs entire space toma1 NTFS
is a file or a portion of the file. The basis of that NTFS is the primary table
files (Master File Table, MFT), which contains at least one entry for each file
volumes, including a record for itself. Each record MFT has a fixed length,
depending on disk, 1.2 - or 4 KB. For most discs used today, the record MFT is 2
KB, which we will continue to take the size of your default. All files on the
NTFS that identifies the file number, which is determined by the position of the
file in MFT. This is similar to file identification method used in the file
system and s5 ufs, which clearly identifies the file number of entries in the
index descriptors. All that NTFS is a sequence clusters that distinguishes it
from the file system discussed earlier, where clusters of shared only data.
Number cluster that NTFS is the logical number cluster (Logical Cluster Number,
LCN). File NTFS also consists of the sequence clusters, the number cluster of
the file is a virtual cluster number (Virtual Cluster Number, VCN). one Windows
NT logical partition call volume. The basic unit of disk space for the file
system, NTFS continuous area clusters, called segments. As a segment addresses
NTFS uses logical number of the first cluster, as well as the number of clusters
in the stretch k, the couple (LCN, k). Thus, part of the file placed in the leg
and begins with a virtual cluster VCN, the address is made up of three numbers:
(VCN, LCN, k). To keep numbers cluster in NTFS used 64-bit pointers, enabling
support files and volumes up to 264 clusters. When the cluster size in 4 KB it
allows files and volumes, consisting of 64 billion kilobytes. NTFS structure
that is shown in Fig. 7.19. Boot block was near the top of NTFS volumes, and a
copy in mid-volume. Boot block contains the standard BIOS parameter block, the
number of units in volume and the number of logical initial cluster mostly
copies and MFT mirror any MFT. Next is the first time in MFT containing 16
standard established in formatting your system files on NTFS. Designation of
these files is described in the table shown below MFT. In NTFS file located in
your table MFT, as its size makes. In the same case, when the file size is more
than size MFT record, in your place only some attributes of the file, and the
remainder of the file is placed in a separate section volume (or more segments).
Part of the file, posted record in the MFT, is part of the resident, and the
remaining part-resident. The home of segments containing non-resident part of
the file, located in the attributes of the resident. Some system files are full
of resident and non-resident, and some have, which are the first segment MFT.
Zero MFT record contains a description of the MFT, including its important
attribute such as the addresses of all its segments. After formatting MFT is a
single segment, but after an erratic first file to store its attributes required
another stretch, as originally continuous sequence clusters MFT has been
completed system files. From the description shows that the MFT itself table as
a file to which method is applicable in that location as a set of randomly
located several segments. NTFS File Structure Each file and directory on NTFS
volume consists of a set of attributes. It is important to note that the file
name and it is also seen as attributes of the file, an interpretation NTFS
attributes of the file, but no other components. Each attribute NTFS file
consists of fields: type attribute length attribute attribute, and perhaps the
name attribute. Type attribute length and the name of a title attribute. There
is a systematic set of attributes defined structure that NTFS. System attributes
have fixed their names and codes, as well as a format. There may also apply
attributes defined by the users. Their names, types and formats are defined
exclusively user. Attributes files sorted by decreasing code attribute, the
attribute of the same type can be repeated several times. There are two ways to
store file attributes-resident deposit accounts in the table MFT and
nerezidentnoe storage outside in the external segments. Thus, the resident
portion of a file is a resident attributes, and nerezidentnaya from resident
attributes. Sorting can be done only by the resident attributes. System kit
includes the following attributes: Attribute List (list of attributes), a list
of attributes that make up a file; references to the number of entries MFT, the
location of each attribute; this rarely used attribute needed only if the file
attributes are not sufficient in basic record and took additional entries MFT;
File Name (name), this attribute contains a long file name in Unicode format, as
well as the number entering the MFT table for the parent directory; if the file
appears in several catalogs, then he will have a few attributes like File Name;
this attribute is always must be resident; MS-DOS Name (name MS-DOS), this
attribute contains the filename of the 8.3; Version (Release) - attribute
contains the latest version of the file number; Security Descriptor (security
descriptor), this attribute contains information about file protection: a list
of access ACL (access to the file are discussed below in the section "Controlling
access to the files") and field audit, which determines what kind of operation
on the file you want register; Volume Version (that version) version that is
used only in the system files that; Volume Name (name of volume) is the name
of that; Data (data) provides normal data file; MFT bitmap (bit map MFT),
this attribute contains a map of units at that; Root Index (root index) -
Finally tree roots used to search files in the directory; Index Allocation (of
the index), non-resident part of the index list Finally tree; Information
Standard (Standard information), this attribute keeps the rest of the standard
file information that is difficult to associate with any of the other file
attributes, such as when a file is being updated, and others. NTFS files
according to the deployment divided into small, large, very high and extreme.
Small files (small). If the file is small, it may be entirely within a single
record MFT, which, for example, the size of 2 KB. Small NTFS files consist of at
least the following attributes (see Figure 7.20): Standard Information (SI-standard
information); filename (FN - file name); Data (Data); security descriptor
(SD-security descriptor). Due to the fact that the file may have a variable
number of attributes, but also because of the variable size attributes can
certainly argue that fit inside the file listing. But usually files smaller than
1500 bytes placed inside your MFT (size 2 KB).
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