1 Virtualization "Virtualization software makes it possible to run multiple operating systems and multiple applications on the same server at the same time," said Mike Adams, director of product marketing at Vmware Virtualization is a large umbrella of technology and concepts that are meant to provide an abstract environment – whether virtual hardware or an operating system – to run applications.

Why Virtualization? Increased performance and computing capacity Underutilized hardware and software resources Lack of space Greening initiatives Rise in administrative costs 2

Charateristics Cloud Computing 3 Virtualization Layer Virtual Hardware Virtual Networking Virtual Storage Software Emulation Host Physical Hardware Physical Storage Physical Networking Guest Applications Virtual Image

Cloud Computing 4 Aggregation Sharing Emulation Isolation Virtualization Physical Resources Virtual Resources ● Increased Security ● Managed Execution ● Portability Characteristics continued ……

Cloud Computing 5 Taxonomy of Virtualization Techniques Virtualization Execution Environment Storage Network …. Emulation High-Level VM Multiprogramming Hardware-assisted Virtualization Hardware-assisted Virtualization Process Level System Level Paravirtualization Full Virtualization How it is done? Technique Virtualization Model Application Programming Language Operating System Hardware Partial Virtualization

Cloud Computing 6 Libraries API ABI Hardware Operative System ISA Applications Operative System Hardware Libraries Applications API calls System calls ISA User ISA User ISA Machine Reference Model Execution virtualization

Security rings and privilege modes Cloud Computing 7 Ring 3 Ring 2 Ring 1 Ring 0 Least privileged mode (user mode) Privileged modes Most privileged mode (supervisor mode) Execution modes Supervisor mode(Master/kernel) Used by OS/hypervisor (runs above supervisor mode) Sensitive operations on hardware level resources User mode Restrictions on machine resources

Hardware – level virtualization 8

Hypervisor 9 ABI Hardware Operative System ISA Virtual Machine Manager ISA VM Hardware ISA Virtual Machine Manager ISA VM Type 2 Type 1 Properties of VMM Equivalence Resource Control Efficiency

Hypervisor Reference Architecture 10 Virtual Machine Manager ISA Virtual Machine Instance Instructions (ISA) Interpreter Routines Interpreter Routines Interpreter Routines Interpreter Routines Allocator Dispatcher

Theorems proposed by Propek and Goldberg 11 Theorem 1: For any conventional third-generation computer, a VMM may be constructed if the set of sensitive instructions for that computer is a subset of the set of privileged instructions. User Instructions Sensitive Instructions Privileged Instructions

Continued.. 12 Theorem 2: A conventional third-generation computer is recursively virtualizable if ● it is virtualizable, and ● a VMM without any timing dependencies can be constructed from it. Theorem 3: A hybrid VMM may be constructed for any conventional third generation machine, in which the set of user sensitive instructions are a subset of the set of privileged instructions.

Hardware Virtualization Techniques 13 Hardware-assisted Virtualization Originally introduced in IBM System/370 x86 architecture did not meet the Popek and Goldberg virtualization requirements. Specific limitations Inability to trap on some privileged instructions. To compensate for the architectural limitations we have Full Virtualization Paravirtualization Partial Virtualization

Continued OS Level virtualization Programming level virtualization Application level virtualization Interpretation Binary translation 14

Other types of Virtualization Storage pooling of physical storage from multiple network virtually into single storage managed from central console. Storage area networks (SANs). Networks splitting up the available bandwidth into channels Assigned/reassigned to a particular server or device in real time. Execution environment 15

Disadvantage Performance degradation Latencies and delays Communication overhead Inefficiency and degraded user experience Insufficient features – emulator cannot replicate certain features Degraded experience : default Hardware mapping Security holes and new threats Phishing Hardware virtualization : malicious thin VMM Ex. BluePill – AMD family ( moves execution of installed OS within a VM) SubVirt: infects guest OS when rebooted. 16

Technology examples Xen – Paravirtualization VmWare – Full Virtualization Microsoft Hyper - V Cloud Computing 17