1. Virtual Servers

2. VMM • VMM was defined as the software-abstraction layer which partitions a hardware system into multiple virtual machines.

5. Hypervisor • A hypervisor or virtual machine monitor (VMM) is a piece of computer software, firmware or hardware that creates and runs virtual machines. • Two type Hypervisor • Type 1 (or native, bare metal) hypervisors:run directly on the host's hardware to control the hardware and to manage guest operating systems. A guest operating-system thus runs on another level above the hypervisor • Type 2 (or hosted) hypervisors:run within a conventional operating-system environment

6. Two types of Hypervisor

7. Bare Metal • This model represents the classic implementation of virtual-machine architectures; • IBM developed the original hypervisors as bare-metal tools in the 1960s: the test tool, SIMMON, and CP/CMS. CP/CMS was the ancestor of IBM's z/VM. • Modern equivalents include Oracle VM Server for SPARC, Oracle VM Server for x86, the Citrix XenServer, VMware ESX/ESXi and Microsoft Hyper-V 2008/2012.

8. Hosted Hypervisor • With the hypervisor layer as a distinct second software level, guest operating-systems run at the third level above the hardware. VMware Workstation and VirtualBox

9. Thee Virtualization Approaches • Full Virtualization • Paravirtualization • Hardware-assisted Virtualization

10. Full Virtualization

11. Full Virtualization (cont) • guest operating system is not aware that it is residing as a virtual machine on a physical host, therefore no modifications will be made on the OS kernel. • since all the interactions of the virtual machine and the physical hardware are being managed by the VMM or the Hypervisor, the VMM will require their own processing needs. • This means that the physical system must reserve some of its resources for the hypervisor to operate. • An example of full virtualization systems would be Vmware ESX and the Microsoft Hyper-V

12. Paravirtualized

13. Paravirtualization • guest operating systems are aware that they are residing on virtual machines and that they are sharing resources with other VMs. • The VMM in this model does not need a lot of processing power in order to manage the VMs residing on the physical system. • This is due to the fact that each OS on a VM is aware of the needs of the other OS for resources on the physical system. • Paravirtualization modifies the kernel of the OS in order to replace instructions which were not virtualized since, in this method, the hardware is partially simulated. • The replaced instructions in this process are referred to as “hypercalls” which assist in the communication between host operations and the OS of the virtual machine • . Examples: XenServer and IBM z/VM.

14. Hardware assisted virtualization • hardware-assisted virtualization is a platform virtualization approach that enables efficient full virtualization using help from hardware capabilities, primarily from the host processors. • Full virtualization is used to simulate a complete hardware environment, or virtual machine, in which an unmodified guest operating system (using the same instruction set as the host machine) executes in complete isolation. • Hardware-assisted virtualization was added to x86 processors (Intel VT-x or AMD-V) in 2006. • Hardware-assisted virtualization is also known as accelerated virtualization;  • Xen calls it hardware virtual machine (HVM), andVirtual Iron calls it native virtualization.

15. Reduce costs by consolidating services onto the fewest number of physical machines http://www.vmware.com/img/serverconsolidation.jpg

16. VPS • A virtual private server (VPS) is a virtual machine sold as a service by an Internet hosting service.[1] • A VPS runs its own copy of an operating system, and customers have superuser-level access to that operating system instance, so can install almost any software that runs on that OS. • For many purposes they are functionally equivalent to a dedicated physical server, and being software defined are able to be much more easily created and configured.

17. Non-virtualized Data Centers • Too many servers for too little work • High costs and infrastructure needs • Maintenance • Networking • Floor space • Cooling • Power • Disaster Recovery

18. Dynamic Data Center • Virtualization helps us break the “one service per server” model • Consolidate many services into a fewer number of machines when workload is low, reducing costs • Conversely, as demand for a particular service increases, we can shift more virtual machines to run that service • We can build a data center with fewer total resources, since resources are used as needed instead of being dedicated to single services