Secondary memory is a type of storage that is used to store data permanently, even when the computer is turned off.
Examples of secondary memory devices include:
hard disk drives
solid state drives
USB flash drives
optical discs
Secondary memory
Why is Secondary Memory Important?
Secondary memory is important because it allows users to store large amounts of data that may not fit in the computer's main memory (RAM). It also allows data to be retained even when the power is turned off, making it ideal for long-term storage.
Examples of secondary memory include and SSD.
Primary vs Secondary Memory Characteristics
Primary Memory
Located on the motherboard
Stores data that is currently being used by the CPU
Is volatile - data is lost when power is turned off
Examples include RAM and cache memory
Secondary Memory
Located outside of the computer, such as hard drives and USB drives
Stores data for long-term use, even when power is turned off
Is non-volatile - data is retained even when power is turned off
Provides more storage capacity than primary memory
Secondary memory is slower than .
Sequential access storage devices
Sequential access secondary storage devices read and write data in a linear, ordered sequence.
Access Time
Generally slower for specific data retrieval because the device must go through a sequence to reach the desired location. However, they can be efficient for reading or writing large, contiguous blocks of data.
Use Case
Best suited for applications that process data in a sequential manner, such as backups, archival storage, and certain types of data streaming.
Cost and Capacity
Typically offer high storage capacities at a lower cost per gigabyte, making them economical for bulk data storage.
Durability
Often designed to handle long-term storage and can be very durable, especially in controlled environments.
Sequential access storage devices read data in a order.
Example of sequential storage devices
Magnetic Tape Drives
Used for backup and archival purposes. Data is written and read in a linear fashion, making it efficient for sequential operations but slow for random access.
Optical Discs (e.g., CDs, DVDs)
Although not purely sequential, accessing non-contiguous data can be slower compared to hard drives or SSDs.
An example of a sequential access storage device is a drive.
Direct (Random) Access Storage Devices
Direct access storage devices allow data to be read or written at any location without the need to proceed sequentially through other data.
Access Time
Faster for retrieving specific pieces of data since the device can jump directly to the desired location.
Use Case
Ideal for applications requiring frequent, non-linear data access, such as operating systems, databases, and file systems.
Cost and Capacity
Generally more expensive per gigabyte compared to sequential storage, but prices have been decreasing, especially for HDDs and SSDs.
Durability
Varies by type, with SSDs generally being more durable than HDDs due to lack of moving parts.
A hard disk drive is an example of a direct access storage device that allows for quick retrieval of data from any on the disk.
