Computer - Storage Device (Media)

About

A storage device is a Computer - Device that stores byte:

• machine instructions byte
• data byte

It is an array of circuits that saves bit state (0 or 1). A storage device can be anything that can store and retrieve 0 and 1.

It's also referenced as:

• data-storage component.
• storage device.
• media

Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data used for computing for some interval of time.

They basically serve I/O request .

Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.

In contemporary usage:

• memory usually refers to a form of semiconductor storage known as random-access memory (RAM) and sometimes other forms of fast but temporary storage.
• storage today more commonly refers to mass storage — optical discs, forms of magnetic storage like hard disk drives, and other types slower than RAM, but of a more permanent nature.

The purpose of a data storage component in the computer world is to store items (data) and allow easy access to them as shelves storage in the real world.

A data storage component is a computer components where data are recording (storing) such as:

• cpu registers and cache
• ram
• floppy disks,
• hard disks,
• CD-ROMs (optical discs)

They are differentiated

• via the memory hierarchy (main/auxiliaire - internal/external - primary/secondary/tertiary)
• and/or by evaluating certain core characteristics

Type of data storage

The storage component can be differentiated by their characteristic or properties but to simplify, there are three main or basic characteristics:

• Latency: how much time it takes between making a request and receiving the data requested
• Capacity: how much it can hold (remember)
• Throughput: how fast can this data be retrieved or stored

Based on the above characteristics, in a typical computer there are four physical types of data storage device (known as memory hierarchy):

• CPU registers – this is were the CPU manipulates the data – no latency, very low capacity
• CPU cache – memory direct access to the CPU unit – some latency for requesting memory
• RAM – some noticeable latency associated with accessing this memory but in the same time, significantly larger capacity
• Disk – significant latency – very large capacity (in database world). This is also sometimes referred to as “main storage” as it is the only non-volatile memory. That is memory that does not get reset on computer shut-down.

A modern computer uses sophisticated rules and techniques to manage these. Typically the hardware manages the CPU cache automatically, and the software controls how CPU registers, RAM, and Disk are used. The CPU registers are a bit more special, as usually they are not dynamically controlled. Rather when a given program is compiled, it has a built-in specific CPU registers usage.

Documentation / Reference

• wiki/Computer_data_storage
• wiki/Data_storage_device