Organization of the file system
Block Size A logical block size plays an important role. In some systems (Unix),
it may be raised during formatting. The small size of the block would result in
each file will contain a lot of blocks. Reading block by delays in the search
and rotation, thus many of the file blocks to be read slowly. Large blocks
provide higher speed exchange with the disk, but because of internal
fragmentation (each file takes integer units, and an average of the last half of
the block disappears) reduced the percentage of useful disk space. In systems
with the organization of memory page has a similar problem with the size of the
page. Studies have shown that most of the files have a small size (in Unix
approximately 85% of files are less than 8 KB size and 48% less than 1 kb). Fig.
12.5 shows two curves: one shows a decreasing degree of recycling drive (as a
percentage) with the growing size of the block, and the second-increasing speed
reader information. They intersect in the region of 3 K. Normal compromise
choice block of 512 B, 1 K, 2 K. The structure of the file system on drive
Consideration of the working methods of disk space gives a general idea of the
office together, the data needed to describe the file system. The structures of
the file system data model, such as Unix, in one of the disk, thus, may consist
of 4 major parts: At the beginning of the section is superblock that contains a
general description of the file system, such as: Type of file system The
size of the file system in the blocks The size of the array index nodes The
size of the logical unit I.t. e. Described data structures are created on the
disk from its formatting (such as utilities format, makefs, etc.). Their
presence offers data on the disk as a file system, rather than as a normal
sequence of blocks. In modern OS file systems to improve the sustainability
superbloka supports multiple copies. In some versions of Unix superblock also
included data structures that control the distribution of disk space, resulting
in superblock continuously subjected to modification, reducing the reliability
of the file system as a whole. Allocation of data structures, describing disk
space, in a separate part is a correct decision. Array index nodes (ilist)
contains a list of indices relevant files of the file system. The size of the
array index is determined by the administrator of knots when installing the
system. The maximum number of files that can be set up in the file system, the
number of available nodes index.
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