TDC 311Server Virtualization

What is Server Virtualization? Let’s see a video

What is Server Virtualization? (from Whatis.com)

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?

No, mainframes and minis have been doing this for years

IBM mainframes have perfected it

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

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 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 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 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? 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 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 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 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