Primary Storage vs Secondary Storage

 

Primary Storage vs Secondary Storage
Primary storage and secondary storage are two types of storage used in computer systems, each serving different purposes. Here are the key differences between primary and secondary storage:

Primary Storage (RAM):

Also known as main memory or random-access memory (RAM).
It is directly accessible by the CPU and holds data and instructions that are actively being used by the computer.
Provides faster access to data compared to secondary storage.
The contents of primary storage are volatile, meaning they are lost when the power is turned off or during a system crash.
Has limited capacity and is more expensive than secondary storage.
Secondary Storage (Disk):

Includes hard disk drives (HDDs), solid-state drives (SSDs), optical discs, magnetic tapes, etc.
Used for long-term storage of data, files, and software.
Typically larger in capacity compared to primary storage.
Provides non-volatile storage, meaning data remains intact even when power is lost.
Slower access speeds compared to primary storage but offers larger storage capacity at a lower cost.
Mechanism for Reading/Writing Data to Disk
Reading and writing data to the disk involves several steps and mechanisms. Here is a simplified overview of the process:

File System: The file system manages how data is organized and stored on the disk. It provides the structure and metadata necessary for accessing and managing files.

File Allocation: When a file is created, the file system allocates space on the disk to store its data. This space can be contiguous or fragmented across multiple disk blocks.

Buffering: The operating system uses a buffer cache to temporarily store recently accessed disk blocks in memory. This improves performance by reducing the need for frequent disk accesses.

Reading Data: To read data from the disk, the operating system receives a read request that specifies the file location and size. It checks the file system metadata to determine the starting disk block of the requested data. The operating system then retrieves the corresponding disk blocks from secondary storage and stores them in the buffer cache. Finally, it transfers the requested data from the buffer cache to the requesting process.

Writing Data: When data needs to be written to the disk, the operating system receives a write request along with the data to be written. It determines the location where the data should be stored on the disk and transfers it from memory or the buffer cache to secondary storage. The file system updates the metadata accordingly to reflect the changes.

Static Files vs Dynamic Files
Static files and dynamic files represent different approaches to storing and accessing data within a computer system. Here are their differences:

Static Files:

Static files store fixed content that does not change frequently or require real-time updates.
The content of static files remains unchanged unless explicitly modified.
Accessing static files typically involves reading their content directly from secondary storage without any modification or processing.
Dynamic Files:

Dynamic files store content that can change frequently or requires real-time updates.
The content of dynamic files is generated, modified, or processed dynamically based on certain conditions or user interactions.
Accessing dynamic files often involves executing code or scripts that generate or manipulate the file’s content before it is served or used.

The choice between static and dynamic files depends on factors such as the nature of the content, performance requirements, flexibility, and scalability needs of the application.

Reference:

Tanenbaum, A. S., & Bos, H. (2015). Modern Operating Systems (4th ed.). Pearson Education.