Development and Implementation of a File System for Gannet Virtual ...

2.2 File System Background Knowledge
A file system provides the mechanism for storing and accessing data. It consists of
two types of entities. First is collection of files which storing the data. Another one is
directory which organizes set of files inside. Hence, a file system provides a high
level abstraction of file on a system. it provides not only a way to store and organize
data as files, but also a set of function that can be run over files on file system.
This section will describe several techniques for storing file in storage and describe
the structure of directory. Moreover, this section also describes the storage
management of files and directories on a storage device.
2.2.1 Storage Management
The management of disk is a major concern on file system as files and directory
stored on disk. There are two approaches for storing a file. First is dynamic
allocation disk approach by using consecutive bytes of disk space. Every file has
different size of storage space depending on its size. Unfortunately, it has major
drawback. The problem arises when a file grows, as this approach has no support
for enlarge the dynamic block, it needs to be allocated to a new disk space which has
bigger size.
Secondly is fixed allocation storage by dividing disk into fixed-size blocks. However,
the size of fixed blocks is a big issue on file system design. Because, if using small
allocation unit, it means that a file will consist of number of blocks. Writing a file to
disk will consume large overhead as there will be number of allocation block for a
file. Furthermore, reading blocks requires a seek overhead and delay. Hence,
reading and writing a file on small blocks will be slow.
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