Storage Devices

* **Reading/Opening Data = Getting our data back again from the storage location.**

**Backing Storage are often categorised with RAM (Random Access Memory). However, there are significant differences which set these two apart from each other.**

 2) It is volatile- all data will be erased when the computer is switched off
 3) RAM has a fast reading and writing of data.

 ==WHAT IS BACKING UP OF DATA?==
DEFINITION- ***"Backing up is the process of using a storage device to copy files and data to a different storage medium in case of a problem with the original copy".***

***TERMINOLOGY***

* **Storage Device = The hardware that saves (writes) or reads the data from the storage medium. (DVD Player for example)**
* **Storage Medium = The hardware that actualy holds the data. (Memory Sticks, Hard Disk Drives, DVD Disks etc.)**

**FUN FACT- Backups are often stored in a different place to the original copy. This is to protect against irretrievable loss such as damage by fires, floods or theft.**

## **WHY SHOULD WE BACK UP DATA?**

**1) DATA COULD BE LOST DUE TO DAMAGE TO THE ORIGINAL STORAGE DEVICE.**

**2) ORIGINAL DATA COULD BE ACCIDENTALLY WRITTEN OR COPIED OVER.**

**3) HACKERS COULD ILLEGALLY ACCESS DATA AND ALTER OR DELETE IT**.

## **WAYS IN WHICH DATA IS STORED AND READ**

**THERE ARE TWO MAIN WAYS IN WHICH DATA IS STORED AND THEN READ FROM THE DIFFERENT BACKING STORAGE DEVICES:**

**SERIAL ACCESS and DIRECT ACCESS**

**INTRODUCTION**

**SERIAL ACCESS (Sequential)**

* ====**Accesses data by starting at the beginning and then works through bit by bit, in order, until the required information is found.**====
* ====**Used on magnetic tape systems and is very slow.**====
* ====**When information on magnetic tape needs updating, an additional tape is required so that the old data can be merged with the new data.** ====

**DIRECT ACCESS (Random)**

* ====**The computer can calculate exactly where the data has been stored and can go straight to it directly (instant access)**====
* ====**This method is much faster than Serial Access.**====
* ====**When stored information needs updating, the Direect Access device will write the data to the next available space and its position re-calculated by the computer.**====

**BACKING STORAGE MEDIA**

* **"Internal or External devices that are used to store data either temporarily or permanently"**

THERE ARE TWO MAIN TYPES OF STORAGE

* **TEMPORARY STORAGE-RAM WHICH LOSES ITS DATA AS SOON AS THE COMPUTER IS SWITCHED OFF.**
* **PERMANENT STORAGE-HARD DISKS AND OTHER FORMS OF STORAGE WHICH DO NOT LOSE THEIR DATA EVEN WHEN THE COMPUTER IS SWITCHED OFF.**

## **STORAGE CAPACITY**

**STORAGE CAPACITY IS THE MAXIMUM AMOUNT OF DATA THAT THE DEVICE CAN HOLD IN BYTES.**

 BYTE
 KILOBYTE(Kb)
 MEGABYTE(Mb)
 GIGABYTE(Gb)
 TERABYTE

## TYPES OF STORAGE DEVICES

EXAMPLES OF STORAGE DEVICES INCLUDE:

* fixed hard disc
* magnetic tape
* flash memory
* floppy disc
* DVD-ROM
* CD-ROM

**MAGNETIC STORAGE**

**DEFINITION-**Magnetic storage media and devices store data in the form of tinymagnetised dots. These dots are created, read and erased using magnetic fields created by very tiny electromagnets

.
**1) FIXED HARD DISC-** *Fixed hard discs are used on all computers and are the main mehod of storing data. The disc surface (Platter) is coated in a magnetic film which is where the data is stored. These have read/write heads which allowe data to be written to (saved) or read (used) from the disc. It is normally used to store the Operating System and Applications Software( Windows, Woed, Excel etc.) It is also used to store Files and Documents (music and homework for example)*

**2) PORTABLE HARD DISC DRIVES-** *Works in a similar way to fixed hard discs but are connected to the computer externally via a Universal Serial Bus (USB) port. Portable Disc Drives are designed to be transportable. It is used as a portable back-up system to abvoid loss of data.*

**3) FLOPPY DISC DRIVES-** *Old method of external data storage where information is held on a thin plastic disc which rotates. As the disc rotates, a read/write head is used to add or read data. Maximum storage on a floppy disc is about 1.44Mb. Floppy discs are still used where very small files need to be transferred/stored (e.g. small word processed documents)*

**4) MAGNETIC TAPES-** *Thin strip of magnetic plastic which is wrapped onto a reel. Data is stored on the magnetic plastic in the form of 1's and 0's (binary). Magnetic tapes are used where extremely large amounts of data need to be backed up. It is also used in Batch Process applications such as clearing bank cheques and producing payslips.*

**OPTICAL STORAGE**

**DEFINITION- Optical Storage Devices are all those mediums that use light tor ead/write the information.**

**1) CD-ROM AND DVD-ROM- CD-ROMS AND DVD-ROMS are classed as Read Only Memory. This means that the data cannot be written over (added to) and can only be read. CD-ROMS are used by manufacturers to store smaller files such as Word Documents and music files while DVD-ROMS are used to store bigger files such as movues and larger games such as COD>**

**2) RECORDABLE CD-R AND DVD-R- Once the disc as been recorded on it, it becomes a CD/DVD ROM (Read Only). Data is 'burned' onto the discs using a special drive (disc burner). Data can be added onto the disc but NOT erased. It is used to create home recordings of music and movies.**

**3) RECORDABLE CD-RW AND DVD-RW-** *Unlike cd/dvd-r's thse discs DO NOT become ROMS (not read only). The dye used to record data is 'special' and it allows the bumps of data to be 'undone' (which erases the data). This process of allowing bumps of data to be erased is known as 'Phase Change'. This particular disc is used in Closed Circuit Television (CCTV) tp allow security to keep an eye on businesses and what is happenign on the streets.*

**4) DVD-RAM-** *Writing and Reading of data can happen at the same time. This means that you could watch a programme at the same time that another is being recorded. This particular disc is used in recording devices such as satellite receivers (SKY TV) to allow simultaneous recording and playback.*

**5) BLU-RAY DISCS-** *BLU RAY discs work in a similar way to DVD ROMS but the laser used to read the data us Blue rather than Red (Red lasers are used to read the other disc types). Blue lasers are capable of reading data dots that are positioned closer together on the disk surface. As a result, more data dots can be stored and read. It is used to store High Definition Videos and is also used to back up Hard Disk Drives in PC's.*

**SOLID STATE STORAGE**

**DEFINITION- Solid State Devices are devices which do not have any moving parts such as reels of tapes, spinning disks, no moving laser beams etc.**

**1) MEMORY STICKS/PEN DRIVES-** *Memory sticks are small, portable external Storage Devices. Memory Sticks use Solid State Technology and are usually connected to the computer via USB ports. Data can be quickly read (used) or written (updated) to the drive. It is used for easily transporting files/data between computers. It is also used for backing up data quickly and easily.*

**2) SECURE DIGITAL CARDS- These are a form of Electronically Erasable Programmable Read Only Memory (EEPROM). It is also known as Secure Digital Cards (SD Cards).**

* **SD Cards current maximum capacity= 64 Gigabytes**
* **Micro SD Cards current max capacity= 32 Gigabytes**

**SD Cards are usually used to store photos on digital cameras, used in mobile phones as memory cards, used by MP3 players to store music files and are also used in hand held devices (like PDA's) to store files and data.**

## **STORAGE DEVICE CAPACITY -OVERVIEW**

**FLOPPY DISC- 1.44 MB**

**CD-ROM- 800 MB**

**DVD-ROM- 4.7 GB**

**SD CARD- 64 GB**

**USB MEMORY STICK- 64 GB**

**BLU-RAY DISC- 100GB**

**MAGNETIC HARD DRIVE- 3 TB**

**MAGNETIC TAPE- 5 TB**

DONE BY **IAN ROMEO**