# Basic CS [3i Infotech Placement]: Sample Questions 88 - 90 of 243

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## Question 88

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### Describe in Detail

Essay▾

What is logical volume group?

### Explanation

• Logical volume group or LVM A relatively new approach to UNIX disks and file systems.
• Provides abstraction layer between operating system and physical hard drives.
• Provides a virtual disk space which can be flexibly mapped to real physical disks.
• The commands in LVM are very similar to the actual physical disks.

Every valid command is preceded by physical volume and volume group as shown below:

• Physical Volume = pv
• Volume Group = vg
• Logical Volume = lv

• Offer greater flexibility for disk partitioning.
• Size of logical volumes can be modified according to need, while the operating system is running
• Logical volumes can span multiple disks.
• Disk mirroring is often supported, for greater data reliability

## Question 89

Basic CS

### Explanation

Answer is achieved by diving by

 Division by Quotient Remainder (decimal) Remainder (hex) Digit

So,

## Question 90

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### Describe in Detail

Essay▾

What are turnaround time and response time?

### Turn Around Time

• The sum total of waiting time & execution time is known as the turnaround time.
• The time a given process takes from submission to completion.
• Example: order of arrival of process P1, P2, P3 was sequential with each taking 5,15, 10 second respetively.
• First process takes s 5 seconds to finish from submission to completion.
• Second process takes 5 + 15 = 20, seconds from submission to completion- Add 5 because P2 has waited for P1 to finish.
• Same, the third process takes 5 + 15 + 10 = 30 seconds from submission to completion.
• The third process has to wait for both P1 and P2 to finish.
• The average turnaround time is seconds.
• We change algorithm from first come first serve to some other scheduling algorithm.
• We think of the turnaround time as the sum of waiting time and execution time.

### Response Time

• The time from the submission of a request to the time of first response by the CPU.
• The time difference between the issuance of a command and the start of a response to command.
• Deceptively similar to waiting time but it is time the given process takes after leaving the ready state until it gets attention of the CPU depending on which scheduling algorithm.
• Useful in interactive systems for understanding the time between issue of command beginning of the output.
• In other words, it is time difference between arrival and the first execution.

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