Virtualization

Question 1

What is the purposed of Virtualization?

Answer 1

1. Enhance resource sharing by many users at a time
2. Virtualization make replacing and upgrading hardware easy
   3.We can add new devices without rebooting.
   4.Down-time is reduced
   5.Adding new machines is very easy.

Question 2

What are the modes of the operating system?

Answer 2

Kernel mode : CPU instructions are allowed to execute
User mode :
Only allows few instructions to be executed. apps ask the kernel to do the work if user application have to execute an instruction

Question 3

What is the impact of virtualization on system calls and I/O?

Answer 3

System calls takes around 2300 cycles because the cpu issues fault message for every system call.
I/O is a major issue because it is not easily modified/upgraded

Question 4

What the the types of virtualization?

Answer 4

1. Type 1 - Bare metal virtualization: (bare metal )Hypervisor is on the top of the hardware (ring 0)
2. Type 2 - Hosted virtualization: Hypervisor loaded on top of an OS just like an application program.

Question 5

What happens when privilege instructions are executed in full virtualization?

Answer 5

They are trapped because they are executed in the less privileged ring. The hypervisor intercepts the traps and emulates the instructions on the fly.

Question 6

What is Cgroups and what is the main task?

Answer 6

control groups is a feature which limits application to a specific set of resources.
their main tasks are limit resources, isolate resource and audit the utility of resouces

Question 7

What is namespace?

Answer 7

it is a feature in the linux kernel which isolates processes from each others.

Question 8

What are containers?

Answer 8

Containers use the kernel features (cgroups and namespaces). container technology provides environment where the hardware is shared. It is a lightweight Vm. It can get a shell via SSH.
Container solutions allow multiple isolated linux system of same kind on single host.

Question 9

What is docker?

Answer 9

Docker utilizes the container technology by porting containers and replicating containers across environments.

Question 10

What are the docker container states?

Answer 10

Created - restarting - running - paused - exited - dead

Question 11

What is the difference between docker and VM?

Answer 11

1. there is always a guest os in every VM. With docker we only have host os which share among all containers which make them light and increase the boot time.
2. Security-wise are VM better since they are stand-alone with their kernel and security features.
3. Dockers performance is better since the Vm need to load the entire OS to start.
4. Portability: since docker containers dont have seperate OS, they are easily portable meaning that putting them on a different OS wont be a problem. thats not the case with VMs

Question 12

What is VMWare Vsphere?

Answer 12

It virtualizes and aggregates the underlying physical hardware resources of datacenter. It promotes private cloud rather than public.

Question 13

What is VMWare Vmotion and SVmotion?

Answer 13

VMotion enables migration of virtual machines from one host memory to another without down time. Disk and files are stored in shared memory

SVmotion does the same but also moves storage information.

Question 14

What are the modes of virtualization on a hardware level?

Answer 14

1. Full virtualization: Here guest OS works in ring 1 and Hypervisor in ring 0. Guest os is not modified here.
   2.para virtualization: same as full but the OS code is modified. Para avoid unnecessary trapping
   3.hardware assisted virtualization: Here privileged instructions are quickly identified and efficiently executed.