Secondary Storage Devices

Secondary Storage Devices

Types of Secondary Storage Devices

  • Secondary Storage Devices are non-volatile, meaning they retain data even when the computer is switched off.

  • Examples include Hard Disk Drives (HDD), Solid State Drives (SSD), and Optical Disks such as CDs, DVDs and Blu-ray disks.

  • Hard Disk Drives (HDDs) use magnetic surfaces on disks, or platters, to store data. A read-write head on an arm accesses the data while the platters are spinning.

  • Solid State Drives (SSDs) store data on flash memory chips. SSDs have no moving parts, so they are much faster, more durable and reliable than HDDs.

  • Optical Disks such as CDs, DVDs and Blu-Rays store data as tiny pits burned into the surface of the disk by a laser.

Storage Capacity

  • The storage capacity of a device is a key factor when choosing a secondary storage device and refers to how much data a device can store. It’s typically measured in gigabytes (GB) or terabytes (TB).

  • HDDs can store a large amount of data, but less than SSDs. SSDs are smaller and more expensive, but they can store more data and access it more quickly.

Data Transfer Speed

  • Data transfer speed, or the rate data can be transferred from the storage device to the RAM, is another key factor. This is usually measured in megabytes per second (MB/s) or gigabytes per second (GB/s).

  • SSDs are much faster at transferring data than HDDs. Optical disks are usually slower than both HDDs and SSDs.

Durability & Reliability

  • Durability and reliability are key factors in choosing a secondary storage device, particularly for valuable or irreplaceable data.

  • HDDs can be prone to failure due to their moving parts. SSDs, with no moving parts, are generally more durable and reliable.

  • Optical disks are vulnerable to scratches and other physical damage, but can be reliable if properly cared for.


  • The cost of secondary storage devices can vary greatly, based on storage capacity, transfer speeds, and the type of device.

  • Generally, HDDs are cheaper per unit of storage than SSDs. SSDs, however, offer better performance, which can be worth the added expense.

  • Optical disks are inexpensive, but offer lower performance and storage capacity than the other types.