Data Storage: Secondary Storage

This section explores secondary storage, a crucial component of computer systems for persistent data storage. Unlike primary storage (like RAM), secondary storage is non-volatile, meaning it retains data even when the power is turned off.

What is Secondary Storage?

Secondary storage is a type of computer memory that is used to store data and programs persistently. It's designed for long-term storage and typically has a larger capacity than primary storage.

Types of Secondary Storage

Several types of secondary storage are commonly used. Here's a breakdown of the most prevalent:

• Hard Disk Drive (HDD): Traditional storage using spinning magnetic platters.
• Solid State Drive (SSD): Uses flash memory for faster data access.
• USB Flash Drives (Thumb Drives): Portable storage devices using flash memory.
• SD Cards: Commonly used in digital cameras and mobile devices.
• Optical Discs (CDs, DVDs, Blu-ray): Data is stored using lasers to read and write information.
• Magnetic Tape: Sequential access storage, often used for backups.

Comparison of Secondary Storage Technologies

The following table summarizes the key differences between common secondary storage technologies:

Technology	Capacity	Speed	Cost	Portability	Durability
Hard Disk Drive (HDD)	High	Slower	Low	Low	Lower
Solid State Drive (SSD)	Medium to High	Faster	High	Medium	Higher
USB Flash Drive	Low to Medium	Medium	Medium	High	High
SD Card	Low to Medium	Medium	Medium	High	High
Optical Disc (CD/DVD/Blu-ray)	Low to Medium	Slow	Low	High	Medium
Magnetic Tape	Very High	Very Slow (Sequential Access)	Low	Low	High (for archival purposes)

How Secondary Storage Works

Secondary storage devices store data using various technologies. HDDs store data magnetically on rotating platters. SSDs use flash memory chips to store data electronically. Optical discs use lasers to read and write data on a reflective surface. The data is organized into files and folders, which are managed by the operating system.

Accessing Data on Secondary Storage

To access data stored on secondary storage, the data must first be loaded into the computer's primary storage (RAM). This process is called loading or reading. When the computer needs to use data, it retrieves it from RAM and transfers it to the processor for processing. Writing data to secondary storage involves transferring data from RAM to the secondary storage device.

File Systems

A file system is a method and data structure that organizes how data is stored on a storage device. It manages the allocation of storage space, tracks file names, and organizes files into directories (folders). Common file systems include FAT32, NTFS, and exFAT.

Data Storage Capacity

Data storage capacity is typically measured in bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), and terabytes (TB). A byte is a unit of digital information. 1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB, and 1 TB = 1024 GB. The increasing demand for larger amounts of data has driven the development of storage devices with ever-increasing capacities.