3.3 Data Storage

Question 1

What is primary storage

Answer 1

RAM/ROM
Directly accessed by CPU
RAM is volatile
ROM is non-volatile

Question 2

What is secondary storage

Answer 2

HDD/SSD
Not directly accessed by CPU
non volatile
stores data that can be accessed later

Question 3

What is offline storage

Answer 3

DVD, CD, USB, flash memory
non volatile
can be disconnected from the computer

Question 4

What is RAM

Answer 4

Random Access Memory
Primary storage
Stores data/programs/instructions that are currently in use
Volatile
Easily expandable

Question 5

What is ROM

Answer 5

Read Only Memory
Non volatile / permanent
Stores the boot program/BIOS 
Used to boot up the computer when it is switched
Fixed size

Question 6

What is virtual memory

Answer 6

When the RAM is full a section of the hard disk is used to store items in RAM that are currently not being used
This frees up space for new programs to be loaded
Slower than RAM

Question 7

What is cache memory

Answer 7

Temporary storage area between CPU & RAM
Stores frequently used instructions/data
Faster as data doesn’t need to be fetched from RAM
Uses faster SRAM
More expensive than RAM

Question 8

What is the difference between DRAM and SRAM

Answer 8

Dynamic RAM:
-Capacitors hold each bit of memory
-Need to be constantly refreshed with power to store bits
-Less expensive, higher storage capacity
Static RAM:
-‘flip-flops’ hold each bit of memory
-No need to refresh power
-Faster and consumes less power

Question 9

Magnetic Tape

Answer 9

Type of magnetic storage
Serial access medium – need to start reading from the beginning
Mainly used for cold storage
Pros: large capacity, cheap, takes up little physical space
Cons: slow to transfer

Question 10

Hard Disk Drive

Answer 10

Magnetic Storage
Data is stored on magnetic platters
Data is created by magnetizing particles on the disk
North and South represent 1s & 0s
Several platters with 2 surfaces spinning thousands of times a second
Disk heads on mechanical arms to read and write data

Question 11

SSD

Answer 11

Solid State Drive
Flash memory and is non volatile 
No moving parts 
Type of EEPROM
Used in phones/cameras

Question 12

SSD vs HDD

Answer 12

Price: SSDs are about 10 times more expensive than HDDs per MB
Power HDDs use about 3 times more battery power than SSDs
Capacity SSDs generally have a much smaller capacity then HDDs
Portability SSDs are smaller and lighter than HDDs
Speed SSDs are almost twice as fast at reading and writing
Noise SSDs are silent whereas HDDs make spinning disc sounds
Durability SSD has no moving partss and is not vulnerable to knocks
Reliability Both are highly reliable, but …. HDD has greater longevity for r___/wr___ functions

Question 13

How is data written to optical storage media e.g CD

Answer 13

The disc is rotated 
A laser beam is used 
The laser beam makes pits and lands 
The data is written in concentric tracks 
The pits and lands represent 1s and 0s

Question 14

CD vs DVD

Answer 14

DVD has a larger capacity
Shorter laser wavelength
… means pit/land size is smaller so more data in the same space
Uses dual layering so there are 2 recording layers

Question 15

DVD-R, DVD-ROM, DVD-RW

Answer 15

DVD-R: recordable, fills up overtime then read only
DVD-ROM: Read only
DVD-RW: rewritable

Question 16

What is DVD-RAM

Answer 16

Concentric tracks opposed to 1 spiral track
Simultaneous read and write operations …up to 100 000 times
Great longevity -> ideal for archiving
Similar operation to HDD

Question 17

Blue ray vs DVD

Answer 17

Blue Ray: 
    -Blue laser 
    -Larger storage capacity 
    -Single polycarbonate layer 
    -Faster transfer rate 
DVD: 
    -red laser 
    -smaller storage capacity 
    -2 polycarbonate layers

Question 18

What is Cloud Storage?

Answer 18

• A method of data storage where data is stored on remote servers
• When data is saved it is sent across the Internet to a server
• It may be stored on more than one server in many locations

Question 19

Give examples of where cloud storage is used

Answer 19

• Data backup, meaning data is not lost if local computers break down
• Shared ‘live’ files for group work, to allow many people to work on the same file at the same time
• Photo and video uploads, for easy access and sharing, and to free up mobile phone storage
• Streaming services, particularly for music, video and gaming

Question 20

What are the 3 different systems of cloud storage?

Answer 20

• Public - This is a storage environment where the customer/client and cloud storage provider are different companies
• Private - This is storage provided by a dedicated environment behind a company firewall; customer/client and cloud storage provider are the same
• Hybrid - This is a combination of the two above environments; some data resides in the private cloud and less sensitive/less commercial data can be accessed from a public cloud storage provider.

Question 21

What are the possible benefits of cloud storage?

Answer 21

• offers almost unlimited storage capacity
• if a customer/client has a failure of their hard disk or back-up device, cloud storage will allow recovery of their data
• provides the user with remote back-up of data helping data loss/disaster recovery
• no need to carry an external storage device or even use the same computer to store and retrieve information
• files stored on the cloud can be accessed at any time from any device anywhere in the world provided internet access is available

Question 22

What are the possible drawbacks of cloud storage?

Answer 22

• the potential failure of the cloud storage company is always possible - this poses a risk of loss of all back-up data
• it can be expensive to pay for high download/upload data transfer limits with the internet service provider (ISP)
• costs can be high if large storage capacity is required
• a slow or unstable internet connection could cause problems accessing or downloading data/files

Question 23

Compare the advantages and disadvantages of local vs cloud storage

Answer 23

Accessibility and portability
Cloud - Users can log in and access their data from any computer with an internet connection
Local - Data can only be accessed on the local computer,
Speed
Local - Accessing stored data is very fast.
Cloud - Even with a fast internet connection, this storage will always be slower
Security
Cloud - There is a risk of hardware failure, so users should always have backup copies of data
Local - Any data on the internet is potentially at risk from unauthorised access. However, most cloud service providers have excellent security features.
Capacity
Cloud - Additional storage capacity can usually be added very quickly, simply by upgrading a subscription.
Local - Adding storage capacity may involve buying a new storage device and physically installing it in the computer.
Cost
Cloud - Initials costs may be lower, but there are normally monthly fees, charged per tebibyte (TiB).
Local - Initial costs may be higher, but there are no monthly costs.
Control and privacy
Local - Data is fully under the user’s control. Backing up data is the responsibility of the user – including having multiple copies in multiple locations, and ensuring backups are up-to-date.
Cloud - Data is stored on a remote computer. This could be in a different country and could be subject to different laws, including different privacy laws. Backing up data is the responsibility of the cloud provider.
Environmental
Cloud - There are concerns about the energy use of data centres, which must operate 24/7 to provide users with constant access to their data.