Runs directly on hardware - More secure and more available - Offers better performance to the guests it supports

Runs on top of an OS - Leverages the OS drivers - Often used for desktop development and testing

First commercially available hypervisor (1998) for the x86 platform - Currently market leader in user share and maturity of offerings - Architecture not tied to an OS

Began Cambridge University research project - Currently exists as an open source project and the core has been used by a number of vendors including Citrix & Oracle - Dom0 is primarily based on Linux

models of VM that can be cloned - VM that cant be powered on(read only state) - configured to be 'golden images-a validated and approved combo of OS with patches, corporate, approved utilities

capture entire machine state at a moment in time - allows user to make changes to the VM and then undo them by reverting to snapshot - not used as backup solution due to potential performance issues

Midterm Flashcards by Elouie Ildefonso

Type of Hypervisors

Software that abstracts hardware resources from VM

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A hypervisor…

manages all of the interactions between VM and hardware resources

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Type 1 Hypervisor

Runs directly on hardware

More secure and more available
Offers better performance to the guests it supports

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Type 2 Hypervisor

Runs on top of an OS

Leverages the OS drivers
Often used for desktop development and testing

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VMware ESXi

First commercially available hypervisor (1998) for the x86 platform

Currently market leader in user share and maturity of offerings
Architecture not tied to an OS

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Xen

Began Cambridge University research project

Currently exists as an open source project and the core has been used by a number of vendors including Citrix & Oracle
Dom0 is primarily based on Linux

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Microsoft Hyper V

Released 2008, but virtualization was available through Virtual Server 2005
- Similar architecture to Xen

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Virtual machines vs Virtual appliances

VA is a pre-configured virtual machine image, ready to run on a hypervisor

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VA is…

not complete VM platform, but rather a software image containing a software stack desgined to run on VM

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VM is…

emulation of a particular computer system

- operate based on pc architecture and functions of a real pc

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Clones, snapshots, copies and templates

VM composed of…

configuration files that describe virtual hardware (.vmx)

- disk files that contain data (.vmdk)

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Sysprep is..

Windows specific utility that can be used to automate customization of cloned VM (NOT ideal)

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Full Clones are..

replicas of original VM and require same storage space

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Linked Clones uses…

original VM for reference and any changes are kept in a delta disk
- requires less space than FC though cause performance issues

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VM Templates are..

models of VM that can be cloned

VM that cant be powered on(read only state)
configured to be ‘golden images-a validated and approved combo of OS with patches, corporate, approved utilities

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Snapshots..

capture entire machine state at a moment in time

allows user to make changes to the VM and then undo them by reverting to snapshot
not used as backup solution due to potential performance issues

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Snapshot files

.vmsd - contains relevant info about snapshot
- .vmem - contains memory state of VM
- .vmsn - VM snapshot file store the state of the VM at time of snapshot
- .vmdk - child disk files termed sparse disks
Each child (snapshot) disk is designated with a snapshot iteration number

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Snapshots lock original VM disk and…

create child a disk where changed blocks are written.

- when user reverts to snapshot, child disk is erased and changes start again

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Multiple snapshots can…

be taken creating sophisticated branches of development

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Deleting snapshots removes…

the child disk with changes allowing original disk to be written once again

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Virtual Switch vs Virtual network adaptors

Hypervisors can manage virtual internal networks with…

virtual switches-no connection to a NIC or any physical communication port

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VMs connect to virtual switches that are tied to…

physical NICs

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In Xen, virtual switches are handled by…

Dom0 instead of hypervisor

- hypervisor doesnt manage network I/O

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Network attached storage uses…

virtual switches and physical NICs

- should be isolated from user traffic with separate virtual/physical network paths

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Configuration options | VM Network option

Edit>Virtual Network Editor Bridged Connection - tied to the VMnet0 virtual adaptor NAT connection - tied to the VMnet8 virtual adaptor Host-only connection - tied to VMnet1 virtual adaptor

Bridged Network Connection

Each VM has unique IP address that is recognized and reachable from outside host

Hypervisor manages..

the traffic through virtual switches

If installed the hypervisor on a host with multiple NICs, you may...

want to select a specific one | - use pull down menu to select specific NIC

Bridged Network Connection | Virtual Network adaptor is not created so...

Perform ipconfig on host - no VMnet0 it is protocol stack that is bound to the physical adaptor

Go to host. Right click on NIC then properties...

See VMware Bridge Protocol

Network Address Translation

Each VM has unique IP but is not reachable from outside the host - host translates the address for use on outside network and routes responses to correct VM

How long has virtualization been around?

First commercially available hypervisor (1998) for the x86 platform VMware ESXi - first commercial x86 hypervisor developed by VMware in 2001

Advantages of using virtualization

to achieve competitive advantages and save money (1970s) | - Proprietary solutions were expensive and inflexible

Virtualization provides..

large ROIs by removing cost from infrastructure

Hypervisors allow multiple virtual servers to run on a single host, which means...

fewer servers are used and resources are consumed more efficiently

Moore's Law | Processing power doubles...

roughly every eighteen months - coined around processing power - today, applies to many technologies

Guest vs Host | Host system would be the..

primary and first installed OS, if you are using bare metal Virtualization platform like hyper-V or ESX, there really isnt a host OS besides the Hypervisor

Type-2 hypervisor like VMware Server..

host OS is whatever OS those applications are installed into

Guest System is a..

Virtual guest or VM that is installed under the host OS. | - guests are the VMs that you run in your virtualization platform

Host & guest

Parent & child

pCPU vs vCPU | Central Processing Unit uses..

instruction set plus data to perform calculations

pCPU physical CPU

Virtualizing a CPU is actually the hypervisor scheduling slices of time on pCPU

vCPU virtual CPU = 1 physical core though vCPUs arent mapped to..

pCPUs

When planning for resources vCPUs can...

be roughly mapped to a single core

If VM is configured with 4 vCPUs and host has 4 pCPUs, all 4 of the 4 pCPUs need..

to be idle for the VM's work to be scheduled

vCPUs can be adjusted by specifying...

#cores - vCPUs can be hot-added with some OS Different platforms support different amounts of vCPUs in VM

When sizing virtualization host, since single pCPU is not 100% busy...

one pCPU can service multiple vCPUs

In a 4 processor quad core system at 1:1

16 vCPUs can be configured

VM with multiple vCPUs needs to schedult time..

on multiple pCPUs

vCPUs might hinder performance on factors like...

physical resources and CPU contention

Best practice is to configure 1 vCPU to new VM..

and increase if needed rather than start higher

Hyperthreading is an..

Intel technology that provides better CPU utilization

Hyperthreading provides up to..

an additional 30% of performance per CPU, though it appears to double the amount of CPUs

2 prerequisites of hyperthreading

OS must support multiple processors | - OS must support hyperthreading

OVF vs OVA | Open Virtualization Format

Vendor neutral industry standard - cross vendor and cross platform - used for export and import of VM

Open Virtual Appliance/Application

can bundle multiple VMs into one package

Good idea to use NAT when first creating VM since...

It gives time to install anti-virus software and configure security should you change to bridged networking

Host-only network creates an internal only network. It is invisible to systems on...

the physical network - IP is visible by other VMs on internal network - allows you to create private subnet - Built in DHCP server

Lan segments is a private network..

that is shared by other VMs | - a LAN segment can be useful for multitier testing

P2V creates VM using existing..

physical servers as their templates

Hot cloning creates VM while source workload is..

active-no application interruption is necessary

Cold cloning requires application to be inactive

possibly rate of data change is too rapid for P2V to ever complete