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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 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