Storage Devices: Types, Uses, and Comparisons
Optical Drives
Optical drives store data as a series of bumps. The way these bumps reflect a laser beam’s light is used to read the data off the disk.
- CDs are used to hold large files and are ideal for storing music and animation files.
- DVDs have a much larger capacity and are used for storing videos and films.
CD-ROM (Compact Disk Read-Only Memory)
Used for the distribution of software and music. With CD-ROM, data is read-only.
DVD-ROM (Digital Versatile Disk Read-Only Memory)
Used for the distribution of movies where you can only read the data off the disk. A DVD-ROM can also be used for reading data off a CD.
Fixed Hard Disks
Used to store operating systems, application software, and any files of data needed by the user. All of this requires that the data can be both accessed and stored onto the media quickly.
Fixed hard disks are fixed in the computer and are not designed to be portable. Portable hard disks are available and will be looked at later.
Fixed hard disks are used for online processes. Many of them are used in file servers for networks.
Advantages of fixed hard disks: high access speed, high transfer rate, high storage capacity.
Disadvantages: cannot be transferred, cannot be taken out of the computer and locked away for security purposes.
Portable Hard Disks
It is possible to buy additional hard disks, which may be removed each night and stored safely.
Also used to store very large files which need to be transported from one computer to another. Generally, they are more expensive than other forms of removable media.
Also used for reasons other than the backup of data and programs.
Advantages: large storage capacity, very fast at accessing and storing files, can be attached to and used by any computer that has a USB port.
Disadvantages: easily stolen, easy for employees to copy confidential data, the danger of viruses being transferred.
Magnetic Tapes
Stores data on a plastic tape coated with a magnetic layer.
Main features: huge storage capacity, used to back up the data stored on hard disks, tape storage is much less common than disk storage.
Used in any application where extremely large storage capacity is needed and the speed of access is not important.
Advantage: high storage capacity means full-length movies can be stored.
Disadvantages: the user cannot store their files on the disk, older computers may not have a drive capable of reading DVDs.
CD-R (CD Recordable) / DVD-R (DVD Recordable)
CD-R allows data to be stored on a CD, but only once. DVD-R allows data to be stored on a DVD once.
CD-RW (CD Rewritable)
A CD-RW disk allows data to be stored on the disk over and over again.
Advantages: re-writable so can be re-used, the data stored can be altered.
DVD-RW (Digital Versatile Disk Read/Write)
A DVD-RW drive can be used to write to as well as read data from a DVD.
Blu-ray: much higher storage capacity than a DVD.
Memory Sticks/Pen Drives
Offer large storage capacities and are ideal media for photographs, music, and other data files. Memory sticks are more expensive per GB than CD/DVD.
Storage Devices and Media
Data needs a material on which to be stored, which is called the storage media. This could be magnetic, optical, or solid-state in the case of a memory card. The storage device is used to record the data onto the media or read it from the media.
Main Internal Memory and Secondary Memory
Main internal memory is of two types: ROM (Read-Only Memory) and RAM (Random Access Memory).
- ROM: permanent, non-volatile, used for boot routines.
- RAM: temporary, volatile, used to hold the operating system, the software in use, and the files currently being worked on.
Advantages: small and lightweight, large storage capacity.
Disadvantages: easily stolen, often left in the computer by mistake and lost.
Flash Memory Cards
Flash memory cards are the small, thin, rectangular or square removable cards that are used for the storage of digital images by digital cameras. They can also be used in any situation where data needs to be stored and so are used with desktop computers, laptops, palmtops, and mobile phones.
Backups and the Reasons for Taking Them
A backup is a copy of data and program files kept for security reasons. Should the originals be destroyed or corrupted, then the backups can be used.