CSCI 22022: File Systems - Part II

Less efficient due to different block sizes

Random access is easy

Table must be in memory all the time and not suitable for large disks

AKA File Control Block, lists the attributes and disk addresses of the file’s blocks

Less memory required and only in memory if the relevant file is open

Reserve last disk address to Disk block containing additional disk addresses

To point to a new inode which contains the metadata for the file

$ echo 'Hello, World!' > myfile.txt

Contiguous Allocation

High read performances, only seeking the first block is needed

Disk fragmentation

Each block is a pointer to the next block in the file

Random access is slow, as n-1 blocks need to be read to find the n-th block

It leads to disk fragmentation, making it difficult to allocate large contiguous blocks of space

Every block can be used, and files can be allocated non-contiguous blocks

Contiguous allocation stores files in contiguous blocks, while linked-list allocation stores files in non-contiguous blocks

By using the command $ ln myfile.txt my-hard-link

It splits the disk into clusters with unique id numbers and uses a table to track what part of what was stored in each cluster.

Limited support for access control and file permissions, limited support for long file names, and fragmentation issues.

The maximum file size is 4 GB and the partition size cannot exceed 8 TB.

NTFS is a journaling file system used in modern Windows operating systems, supporting access control lists (ACLs) and control over file and folder permissions.

Journaling keeps track of changes not yet committed to the file system.

ACLs are used to control access to files and folders, allowing administrators to assign permissions to individual users or groups.

NTFS provides improved security, flexibility, and features compared to FAT32.

To recover file system consistency in the event of a system failure or power loss

256 TB

High-performance and scalability

Performance and scalability

Enhanced performance and strong encryption

Minimized duplication of code

Extents replace the traditional block mapping scheme

Data protection

The main components of a file system are Application Programs, Logical File System, File-Organization Module, Basic File System, I/O Control, and Devices. These components interact with each other to manage files, directories, and storage devices, providing a layered architecture for file system management.

The primary function of the Logical File System layer is to manage metadata, such as file names, sizes, and permissions, and to maintain the file structure using file-control blocks (i-nodes).

The File-Organization Module is responsible for managing files and their logical blocks, and includes a free space manager that tracks unallocated blocks and provides them to the file-organization module when requested.

The Basic File System layer issues generic commands to the appropriate device driver to read and write blocks on the storage device, and manages the memory buffers and caches that hold various file system, directory, and data blocks.

The I/O Control layer consists of device drivers and interrupt handlers that transfer information between the main memory and the disk system, and manipulate the physical device to read and write data.

A file system is a layer of software that manages files and data on a storage device, while a storage device is the physical mechanism that stores the data, such as a hard drive or solid-state drive.

The Application Programs layer consists of the day-to-day programs that are run by the user, such as web browsers and text editors, and provides a interface to the file system for the user.

The file system manages the allocation of disk space to files through the File-Organization Module, which tracks unallocated blocks and provides them to the file-organization module when requested, and the Logical File System layer, which manages metadata and maintains the file structure.