By: Abhishek Srivastava

STORAGE DEVICES

Introduction to Storage

Computer data storage, often called storage or

memory, is a technology consisting of computer

components and recording media used to retain

digital data.

Memory Hierarchy

Storage

Primary Memory

Primary

storage often

referred to

simply as

memory, is the

only one

directly

accessible to

the CPU. The

CPU

continuously

reads

instructions

stored there

and executes

them as

Registers

• These are located inside the processor. Each register typically holds a word of data (often 32 or 64 bits

• Registers are the fastest of all forms of computer data storage.

Cache

• It is an intermediate stage between ultra-fast registers and much slower main memory.

• Most actively used information in the main memory is just duplicated in the cache memory, which is faster, but of much lesser capacity.

Main

• Main memory is directly or indirectly connected to the central processing unit via a memory bus

• It consists of RAM & ROM

Secondary Memory

Secondary

storage differs

from primary

storage in that it

is not directly

accessible by

the CPU. The

computer

usually uses its

input/ output

channels to

access

secondary

storage and

transfers the

desired data

using

intermediate

Magnetic

• It is usually used as secondary storage. The time taken to access a given byte of information stored on a hard disk is typically a few thousandths of a second, or milliseconds.

• It includes tape, Hard disk, floppy Disk etc.

Optical

• An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data.

• It includes CD-R, CD-RW, DVD, Blue ray etc.

Types of Storage Techniques

Magnetic Storage

A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions(i.e. north or

Diskettes (floppy disks)

Hard disks

High-capacity floppy disks

Disk cartridges

Magnetic tape

How Magnetic Memory works ?

Hard Disk Drive

Typically mounted inside the computer

Provides permanent storage and quick access

Stores information either on small disks called platters or in integrated memory chips

Read and write operations are managed by the controller

Data is transferred to and from the motherboard by the host adapter

Floppy Disk Drives Rapidly becoming obsolete

but still found in legacy applications

Most recent configuration accepted a removable 3 1/2" disk with a storage capacity of 1.44 MB

Traditionally assigned drive letters A: and B:

Power supplied through a 4-pin Mini power Connector (Molex)

Data transferred to motherboard through a 34-pin keyed ribbon cable

Optical Storage

Data is recorded to this type of media by stamping irregularities onto the surface of the disc, or "burned" into it using a laser, in a spiral pattern that runs from the inside to the outside of the disk.

Compact Disk

Digital versatile Disk

Blue Ray Disk

How Optical Device works?

Compact Disk

Used for digital data storage

Formats include read-only (CD-ROM), write-once audio and data storage (CD-R), and rewritable media (CD-RW).

Storage capacity ranges from 650-900MB.

DVD

DVD discs can be single or double sided.

each DVD side may contain a second invisible "layer" to increase the disc's storage capacity.

4.7GB capacity(single-sided/single-layer)

8.5GB capacity (single-sided/double-layer)

9.4GB capacity (double-sided/single-layer)

17.1GB capacity (double-sided/double-layer)

Blue Ray Disk

High-density optical disc created with a blue laser

Used to store HD video and large amounts of data

25-50GB storage capacity single-layer

50-100GB storage capacity dual-layer

Flash Memory

Flash memory cards have high-capacity storage laminated inside a small piece of plastic

Flash memory cards do not need a drive with moving parts to operate

Flash Memory Talk

Example

s of Flash

Memory

Compact Flash (CF)

xD-Picture Card (xD)

Smart Media (SM) Card

Secure Digital (SD) card

Multi Media Cards (MMC)

Tertiary Memory

Tertiary storage or tertiary memory, provides a third level of storage. Typically it involves a robotic mechanism which will mount and dismount removable mass storage media into a storage device according to the system's demands; this data is often copied to secondary storage before use.

Examples are Tape libraries& optical juke boxes

Memory Addressing

Memory is a collection of cells, each with a unique physical/memory address

Each cell can hold one byte or 8 bits

The cell contents can change, but the cell address or reference to the cell is always the same.

Storage Memory Terms

= 8 bits

≈ 1 Thousand Bytes

≈ 1 Million Bytes

≈ 1 Billion Bytes

≈ 1 Trillion Bytes

≈ 1 quadrillion Bytes

≈ 1 quintillion Bytes

1 Byte

1 Kilobyte (KB)

1 Megabytes (MB)

1 Gigabytes (GB)

1 Terabytes (TB)

1 Petabyte (PB)

1 Exabyte (EB)

THANK U ALL…