Module 6 Ppt

Question 1

What are the two main categories of storage based on volatility?

Answer 1

Volatile storage and non-volatile storage

Volatile storage loses contents when power is switched off, while non-volatile storage retains contents.

Question 2

What is primary storage?

Answer 2

Fastest media but volatile (e.g., cache, main memory)

Primary storage is essential for quick access to data currently in use.

Question 3

What is secondary storage?

Answer 3

Next level in hierarchy, non-volatile, moderately fast access time (e.g., flash memory, magnetic disks)

Also referred to as online storage.

Question 4

What is tertiary storage?

Answer 4

Lowest level in hierarchy, non-volatile, slow access time (e.g., magnetic tape, optical storage)

Often referred to as offline storage.

Question 5

What is the function of the read-write head in magnetic disks?

Answer 5

Reads or writes magnetically encoded information

Positioned very close to the platter surface.

Question 6

What is a sector in the context of magnetic disks?

Answer 6

The smallest unit of data that can be read or written, typically 512 bytes

Each track on a platter is divided into sectors.

Question 7

What does the disk controller do?

Answer 7

Interfaces between the computer system and the disk drive hardware

It accepts commands to read/write sectors and remaps bad sectors.

Question 8

What is RAID?

Answer 8

Redundant Arrays of Independent Disks

A disk organization technique that manages multiple disks to provide high capacity and reliability.

Question 9

What is the purpose of redundancy in RAID systems?

Answer 9

To store extra information that can be used to rebuild information lost in a disk failure

Techniques like mirroring help prevent data loss.

Question 10

What is RAID Level 1?

Answer 10

Mirrored disks with block striping

Offers best write performance and is popular for applications like log files.

Question 11

What is the main characteristic of RAID Level 0?

Answer 11

Block striping; non-redundant

Used in high-performance applications where data loss is not critical.

Question 12

What is the difference between bit-level striping and block-level striping?

Answer 12

Bit-level striping splits bits of each byte across multiple disks; block-level striping assigns whole blocks to different disks

Block-level striping is more efficient for I/O operations.

Question 13

What is the main benefit of RAID Level 5?

Answer 13

Block-Interleaved Distributed Parity; partitions data and parity among all disks

Provides higher I/O rates and avoids the bottleneck of a single parity disk.

Question 14

What is the P+Q Redundancy scheme in RAID Level 6?

Answer 14

Stores extra redundant information to guard against multiple disk failures

Offers better reliability than Level 5 at a higher cost.

Question 15

What factors should be considered when choosing a RAID level?

Answer 15

• Monetary cost
• Performance
• Performance during failure
• Performance during rebuild

Each RAID level has different implications for these factors.

Question 16

True or False: RAID Level 2 is commonly used today.

Answer 16

False

RAID Level 2 is not used since it is subsumed by Level 3 and Level 5.

Question 17

Fill in the blank: RAID Level 4 uses ________ to keep a parity block on a separate disk.

Answer 17

Block-Interleaved Parity

This allows for higher I/O rates for independent block reads.

Question 18

What is the main drawback of RAID Level 3?

Answer 18

Bit-striping forces single block reads to access all disks, wasting disk arm movement

This inefficiency is why it is not commonly used anymore.

Question 19

What does the term ‘mean time to data loss’ depend on?

Answer 19

Mean time to failure and mean time to repair

Example: MTTF of 100,000 hours and repair time of 10 hours leads to a high mean time to data loss.