11 Physical Representation: Storage and File Structure

Question 1

How is physical storage media classified?

Answer 1

By speed, costs, reliability, and volatility

Classification criteria for physical storage media

Question 2

What does reliability in storage refer to?

Answer 2

Trustworthiness to save data during crashes and failures

Reliability is not the same as volatility

Question 3

What is the difference between volatile and non-volatile storage?

Answer 3

Volatile storage loses contents when power is off; non-volatile persists

Examples of volatile storage include cache and RAM; examples of non-volatile include flash memory and magnetic disks

Question 4

What are the components of physical storage media?

Answer 4

Cache, main memory, flash memory, magnetic disk

Each component has distinct characteristics and uses

Question 5

What is cache in terms of storage?

Answer 5

Smallest and fastest form of storage (< 10ns), volatile, low reliability, expensive

Used to temporarily store data that the CPU needs immediately

Question 6

How does main memory (RAM) compare to cache?

Answer 6

Larger, slower, volatile, expensive, and unreliable

RAM stores data and programs currently being used

Question 7

What are the characteristics of flash memory?

Answer 7

Non-volatile, faster than magnetic disks, slower than RAM, medium costs, reliable

Used in SSDs, USB drives, and devices like phones and cameras

Question 8

What is a magnetic disk?

Answer 8

Non-volatile, slow, cheapest form of storage, reliable

Examples include Hard Disk Drives (HDDs) used in gaming consoles

Question 9

Fill in the blank: Cache is the ________ and ________ form of storage.

Answer 9

smallest, fastest

Cache is located inside the CPU or very close to it

Question 10

True or False: Flash memory is slower than RAM when reading.

Answer 10

False

Flash memory reads equally fast to RAM but is slower on writes/erases

Question 11

What is the access speed range for main memory (RAM)?

Answer 11

10 ns to 100 ns

RAM is faster than magnetic disks but slower than cache

Question 12

What is the primary disadvantage of magnetic disks?

Answer 12

More prone to physical damage due to moving parts

Long use or physical shock can disturb magnetic disks

Question 13

What are disc heads?

Answer 13

Tiny arms that read and write data on the disk, hovering just above the surface.

Question 14

What is a platter in a magnetic disk?

Answer 14

A round flat disk inside the hard drive that spins and stores data, with two surfaces for storage.

Question 15

Define track and cylinder in the context of a magnetic disk.

Answer 15

A track is a circular path on the surface of a platter; a cylinder is a group of tracks that line up vertically across all platters.

Question 16

What is a sector in a magnetic disk?

Answer 16

The smallest physical storage unit on the disk, each track is divided into sectors.

Question 17

What is a block in the context of data storage?

Answer 17

A unit of data that the system reads/writes at once, made up of one or more sectors.

Question 18

True or False: Discs are faster than RAM.

Answer 18

False

Question 19

What are the components of total time (T_Access) to read N bytes?

Answer 19

• T_Seek
• T_Rotational
• T_Transfer

Question 20

How is T_Transfer calculated?

Answer 20

T_Transfer = N / DTR

Question 21

What is RAID?

Answer 21

A technique that uses multiple disks in parallel to offer higher capacity, speed, and high reliability.

Question 22

What is redundancy in RAID?

Answer 22

A backup system used to rebuild data if a disk fails.

Question 23

What is the role of a buffer in data storage?

Answer 23

A portion of RAM used to store copies of disk blocks temporarily.

Question 24

What does a buffer manager do?

Answer 24

Allocates space in the buffer and decides which blocks to load and how to replace them.

Question 25

Define a record in the context of a database.

Answer 25

An individual entry or row in a table.

Question 26

What is a fixed-length record?

Answer 26

Records with a predefined number of fields and fixed value sizes.

Question 27

What is the fastest method to delete a record in a fixed-length record file?

Answer 27

Move the last record to the spot of the deleted record.

Question 28

What are variable length records?

Answer 28

Records where the length of data can vary based on different factors.

Question 29

What issues do variable length records cause?

Answer 29

Growth and deletion challenges, as they can lead to fragmentation.

Question 30

What is the pointer method for variable length records?

Answer 30

A method that connects reoccurring records using pointers to fixed-length records.

Question 31

What is heap organization in file records?

Answer 31

Records can be placed anywhere in the file where there is available space.

Question 32

What is sequential organization in file records?

Answer 32

Records stored in sorted order based on the value of a search key.

Question 33

How does hashing organization work?

Answer 33

A hash function is applied to an attribute of each record to determine its file location.

Question 34

What is multiple clustering organization?

Answer 34

Stores several relations together in one file based on their relationship.

Question 35

What does a data dictionary store?

Answer 35

* Information about relations * User and accounting information * Statistical data * Physical file information * Information about indices

Question 36

What is the tradeoff in data storage media?

Answer 36

Speed vs size.

Question 37

Where is data generally stored in data storage media?

Answer 37

Magnetic discs.