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Hard disk drives record data on spinning magnetic platters; large and cheap, but slower and easily damaged.
CDs, DVDs and Blu-ray discs are read by a laser; portable, but slower and smaller in capacity.
SSDs, pen drives and SD cards use flash memory with no moving parts; fast and shock-resistant.
Files are kept on remote servers and reached over the internet, from anywhere, given a connection.
Weigh capacity, speed, durability, portability and cost against the task.
Storage devices keep data and programs for later use. This section's sub-lesson classifies them as magnetic, optical, solid-state and cloud storage and compares their capacity, speed and uses.
This section has one sub-lesson, Types of Storage Devices. It sorts storage into four groups: magnetic storage such as hard disk drives, optical storage such as CDs, DVDs and Blu-ray discs, solid-state storage such as SSDs, pen drives and SD cards, and cloud storage such as Google Drive and Dropbox. For each group it gives examples and characteristics, so that you can choose the right storage for a task.
Storage devices are the secondary memory of a computer: they keep files, applications and the operating system safe when the power is switched off. The sub-lesson Types of Storage Devices classifies them into four groups and describes each one in turn.
1. Magnetic storage. A hard disk drive (HDD) records data magnetically on spinning platters, read and written by heads on a moving arm. It gives a large capacity at a low cost, but its moving parts make it slower than solid-state storage and easier to damage if it is dropped.
2. Optical storage. CDs, DVDs and Blu-ray discs store data that is read by a laser. They are portable and useful for distributing media and keeping copies, but they are slower than hard disks and SSDs and hold less data.
3. Solid-state storage. Solid-state drives (SSDs), pen drives and SD cards use flash memory, which has no moving parts. SSDs read and write data much faster than hard disks, and all of them stand up better to knocks and shocks, though they usually cost more for the same capacity.
4. Cloud storage. Services such as Google Drive and Dropbox keep files on remote servers that are reached over the internet. Files can be opened from any device and shared easily, and they also serve as a backup, but they need an internet connection, and users must think about the privacy of what they upload.
The sub-lesson ends by stressing that each type suits different needs: choosing storage means weighing capacity, speed, durability, portability and cost for the job in hand.