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TDC 311. Server Virtualization. What is Server Virtualization?. Let’s see a video. What is Server V irtualization? (from

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Tdc 311

TDC 311

Server Virtualization

What is server virtualization
What is Server Virtualization?

  • Let’s see a video

What is server v irtualization from whatis com
What is Server Virtualization? (from

  • Server virtualization is the masking of server resources, including the number and identity of individual physical servers, processors, and OSs, from server users

  • The server administrator uses a software application to divide one physical server into multiple isolated virtual environments

  • Isolated environments aka partitions, guests, instances, containers, or emulations

Is this a new technology
Is This a New Technology?

  • No, mainframes and minis have been doing this for years

  • IBM mainframes have perfected it

Three popular approaches
Three Popular Approaches

  • The virtual machine model

  • The paravirtual machine model

  • Virtualization at the operating system level

  • Let’s examine each of these

The virtual machine model
The Virtual Machine Model

  • Based on host/guest paradigm

  • Each guest runs on a virtual imitation of the hardware layer

  • Guest OS runs without modifications

  • A hypervisor runs on top of the host machine which coordinates guest OS requests to the hardware resources (aka virtual machine monitor (VMM))

  • Hypervisor validates all guest-issued CPU instructions and manages any executed code that requires additional privileges

  • VMware and Microsoft’s Virtual Server use this model

The paravirtual machine model
The Paravirtual Machine Model

  • Also based on host/guest paradigm and uses a virtual machine monitor

  • But here the VMM actually modifies the guest operating system’s code

  • This is called porting

  • Porting supports the VMM so it can utilize privileged systems calls sparingly

  • Xen and UML are examples of this model

Virtualization at the os level
Virtualization at the OS Level

  • Not based on host/guest paradigm

  • Host runs a single OS kernel as its core and exports OS functionality to each of the guests

  • Guests must use the same OS as the host, although different distributions of the same system are allowed

  • This distributed architecture eliminates system calls between layers, which reduces CPU usage overhead

Virtualization at the os level1
Virtualization at the OS Level

  • But each partition must remain strictly isolated from its neighbors so that a failure or security breach in one partition will not affect any other partition

  • Common binaries and libraries on the same physical machine can be shared

  • Virtuozzo and Solaris Zones use this model

Is virtualization for everyone
Is Virtualization For Everyone?

  • No

  • Good to great solution for small- to medium-scale server usage

  • For example, you are taking a 12 GHz server and chopping it into 16 750 MHz servers

  • But if 8 of those servers are in off-peak or idle mode, the remaining 8 servers will have nearly 1.5 GHz available to themselves

Is virtualization for everyone1
Is Virtualization For Everyone?

  • You do not want your processor to exceed 50% utilization during peak loads (simple rule of thumb)

  • Following might be good choices for virtualization:

    • HTTP

    • FTP

    • DNS

    • DHCP

    • RADIUS

    • LDAP

    • File services using Fiber Channel or iSCSI storage

    • Active Directory services

Is virtualization for everyone2
Is Virtualization For Everyone?

  • Potentially bad choices for virtualization:

    • Exchange Server

    • Microsoft SQL

    • MySQL

    • Oracle

    • Any logical server that requires two or more physical servers for operation

Physical to virtual server migration
Physical to Virtual Server Migration

  • Any respectable virtualization solution will offer some kind of physical to virtual (P2V) migration tool

  • This tool will take an existing physical server and make a virtual hard drive image of that server with the necessary modifications to the driver stack so that the server will boot and run as a virtual server

  • Great way to support a disaster recovery plan