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TDC 311

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

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TDC 311

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  1. TDC 311 Server Virtualization

  2. What is Server Virtualization? • Let’s see a video

  3. 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

  4. Is This a New Technology? • No, mainframes and minis have been doing this for years • IBM mainframes have perfected it

  5. Three Popular Approaches • The virtual machine model • The paravirtual machine model • Virtualization at the operating system level • Let’s examine each of these

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

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