Write short notes on:

  1. Linux File System
  2. Resource Allocation Graph

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a) Linux File System

A file system is a set of processes that control how, where and when data is stored and retrieved from a storage device. An efficient file system is essential for everyday system processes.

The Linux kernel supports various file systems, but the most commonly used is the ext4 file system.

The ext file system stands for “Extended File System”. It was the first file system designed to support the Linux Kernel. The ext4 file system is the default file system of the current Linux kernel. It was introduced in October 2008 with Linux kernel 2.6.28.

The ext4 file system supports the maximum file size of 16TiB and restricts maximum filename lengths to 255 bytes. This file system features Backward Compatibility, Timestamp Improvements, Delayed allocations, Unlimited number of subdirectories, Journal Checksums, Online defragmemtation etc.

Limitations of ext4 file system:

Although the ext4 file system is considered as the best file system for Linux distributions, there are a few limitations that should be considered in the further development of the system:

Corrupted data recovery – The ext4 file system cannot detect or recover corrupted data already written on the disk.

Maximum volume size – The maximum volume size is set to 1 EiB. However, the file system cannot address more than 100 TiB of data without a significant loss of performance and increased disk fragmentation.

b) Resource Allocation Graph

The Resource Allocation Graph, also known as RAG is a graphical representation of the state of a system. It has all the information about the resource allocation to each process and the request of each process.

Representation of Resource Allocation Graph (RAG):

  • Like all other graphs, it also has vertices and edges.
  • The vertices of the RAG represent the process or the resource, and the edges represent the allocation or request of any resource.
  • As both the process and resource are the vertices of the graph, generally, the process vertex will be represented using the circle and the resource vertex using the rectangle.
  • The resource can be of two types:
  1. Single Instance – It contains the single instance of the resource, and is represented by a single dot inside the rectangle which is the resource vertex.
  2. Multiple Instance – It contains the multiple instances of the resource, and is represented by multiple (more than one) dots inside the rectangle.
  • Edges also can be of two types:
  1. Assign Edge – This edge directing from the resource towards the process represents the allocation of the resource to the process.
  2. Request Edge – This edge directing from the process towards the resource represents the request of the resource by the process.
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