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os final > chapter 14 - virtual machines > Flashcards

chapter 14 - virtual machines Flashcards

1
Q

what does virtualization do?

A

allows a PC or server to simultaneously run more than 1 OS or more than 1 session of the same OS

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2
Q

what is the history of virtualization?

A

was used during 1970s in IBM, became mainstream in early 2000s when it became commercially available on x86 platform

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3
Q

what is the software for virtualization called?

A

a virtual machine monitor AKA hypervisor

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4
Q

what does a VMM do?

A

acts as layer between hardware and the VMs to act as as resource broker

allows multiple VMs to coexist on single host

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5
Q

what is consolidation ratio?

A

the number of VMs that can run on a host

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6
Q

8 reasons for virtualization

A

legacy hardware, rapid development, versatility, consolidation, aggregating, dynamics, ease of management, increased availability

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7
Q

how does a virtual machine work?

A

configured with a number of processors, RAM, storage resources, and network connectivity.

powered on like a physical server, loaded with an OS, and utilized like a physical server

it is limited to seeing only the resources it has configured

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8
Q

5 hypervisor functions

A

execution management of VMs, devices emulation and access control, execution of privileged operations, management of VMs, administration (hypervisor platform and software administration activities.)

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9
Q

What is a Type 1 hypervisor?

A

runs directly on host hardware like OS would, directly controls host resources

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10
Q

Examples of Type 1 hypervisor

A

VMware ESXI, Microsoft Hyper-V, Xen variants

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11
Q

What is a Type 2 hypervisor?

A

runs on host’s OS, relies on host OS for hardware interactions

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12
Q

Examples of type 2 hypervisor

A

VMware workstation, Oracle virtual box

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13
Q

Type 1 vs Type 2 hypervisors

A

type 1 performs better
type 2 is more secure, can run on a system being used for other things like user’s workstation

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14
Q

what is paravirtualization?

A

software-assisted virtualization technique

OS is modified so that calls to the hardware are replaced with calls to the hypervisor

is faster with less overhead, but you need a modified OS

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15
Q

what is a virtual appliance?

A

consists of applications and an OS distributed as a virtual machine image, independent of hypervisor or processor architecture, can run on type 1 or type 2 hypervisor, deploying this is easier than installing an OS

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16
Q

what is a security virtual appliance?

A

security tool that monitors and protects the other VMs

can monitor state of VM including registers, memory, i/o devices, network traffic

17
Q

what is container virtualization?

A

another approach to virtualization

software running on top of the host OS kernel, all containerized applications on a host share common OS kernel

18
Q

how is container virtualization different from hypervisor VMs

A

containers don’t aim to emulate physical servers

19
Q

what is the benefit of container virtualization?

A

eliminates need for each VM to run its own OS and reduces overhead

20
Q

what are kernel control groups?

A

originally developed for Linux and called process containers later became cgroups

all processes are descendants of the init process forming a single process hierarchy. Cgroups allow for multiple process hierarchies in a single OS

21
Q

4 things control groups provide

A

resource limiting: how much memory is usable

prioritization: some groups can get a larger share of CPU or disk i/o

accounting: used for billings purposes

control: groups of processes can be frozen, stopped, or restarted

22
Q

container advantages

A

By sharing the OS kernel, a system may run many containers compared to the limited number of VMs and guest OSs of a hypervisor environment.

Application performance is close to native system performance.

23
Q

container disadvantages

A

Container applications are only portable across systems with the same OS kernel and virtualization support features.

An app for a different OS than the host is not supported.

May be less secure if there are vulnerabilities in the host OS.

24
Q

What is Docker?

A

provides a simpler and standardized way to run containers, makes it easy to load the container image in a simple and quick manner, stored in the cloud as images

25
Q

2 ways to provides processor resources

A

emulation, schedule time on physical CPUs (pCPUs)

26
Q

emulation advantage and disadvantage

A

adv: emulation software may run on different platforms

disadv: not very efficient

27
Q

virtual processors (vCPUs)

A

number of vCPUs has to be set

on a server without VM support, an application may have access to all resources on the server

when migrating to a VM env, configuring the VM to have the same number of processors as before is wasteful

start with one vCPU and monitor performance, add more if needed

start with <= the number of pCPUs

28
Q

what are protection rings

A

describe the level of privilege granted to the software

29
Q

what are the protection ring levels?

A

ring 0: most trusted, kernel runs here, run hypervisor here

ring 1&2: less privileged, used by device drivers

ring 3: least privileged, user application runs here

30
Q

what is memory overcommit?

A

hypervisor temporarily borrows memory from 1 VM to satisfy the needs of another

balloon driver mechanism

31
Q

what is the balloon driver mechanism?

A

requests memory (inflates) in the guest OS which causes the guest OS to free up pages no longer needed, it then deflates and the freed pages can be used for some other VM short on memory

used if memory is needed

32
Q

what happens if the balloon driver method doesn’t work?

A

last resort, the server can page its own memory to disk

33
Q

I/O virtualization advantages

A

enables hardware independence since the VM sees a more general device. helps with VM migration since new host may not have exact same device

34
Q

VMware ESXi

A

market leader with large set of features and maturity

is type 1 hypervisor

35
Q

Microsoft Hyper-V and Xen variants

A

they are similar in architecture

36
Q

Java virtual machine (JVM)

A

java runs in this

provides runtime space for java program to run on any OS and hardware

37
Q

Linux VServer

A

fast, open source container approach to a virtual machine

is a container scheme

38
Q

VServer Scheduling

A

a token bucket filter overlays the standard Linux scheduler

controls how much processor time each VM gets

Tokens add to the bucket at a rate of R tokens every T interval

execution consumes tokens, when bucket empties, VM is put on hold until it refills to M tokens

os final (5 decks)

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