Unit 3 Virtualization.pdf
- 3. Virtualization • Virtualization is the "creation of a virtual (rather than actual) version of something, such as a server, a desktop, a storage device, an operating system or network resources". • Virtualization is a technique, which allows to share single physical instance of an application or resource among multiple organizations or tenants (customers). It does by assigning a logical name to a physical storage and providing a pointer to that physical resource when demanded. • Creation of a virtual machine over existing operating system and hardware is known as Hardware Virtualization. A Virtual machine provides an environment that is logically separated from the underlying hardware. • The machine on which the virtual machine is going to create is known as Host Machine and that virtual machine is referred as a Guest Machine
- 4. • This virtual machine is managed by a software or firmware, which is known as hypervisor. • Firmware's are generally a type of software used to control hardware devices. • Firmware is a software program or set of instructions programmed on a hardware device. It provides the necessary instructions for how the device communicates with the other computer hardware. • Firmware is typically stored in the flash ROM of a hardware device.
- 6. Implementation Levels of Virtualization • Virtualization is implemented at different levels by resembling specific structures into analogous software that appears to work as the same way as physical structure. The levels upon which virtualization is implemented is shown in figure
- 7. Virtualization at ISA (Instruction Set Architecture) level • Virtualization is implemented at ISA (Instruction Set Architecture) level by transforming physical architecture of system’s instruction set into software completely. The host machine is a physical platform containing various components, such as process, memory, Input/output (I/O) devices, and buses. The VMM installs the guest systems on this machine. The emulator gets the instructions from the guest systems to process and execute. The emulator transforms those instructions into native instruction set, which are run on host machine’s hardware. The instructions include both the I/O- specific ones and the processor-oriented instructions. For an emulator to be efficacious, it has to imitate all tasks that a real computer could perform. • The instructions should be interpreted before being executed. And therefore the system with ISA level of virtualization shows poor performance.
- 8. Virtualization at HAL (hardware abstraction layer) level • This level helps perform virtualization at the hardware level. It uses a bare hypervisor for its functioning. This level helps form the virtual machine and manages the hardware through virtualization. • It enables virtualization of each hardware component such as I/O devices, processors, memory, etc. • The virtualization at the HAL (Hardware Abstraction Layer) is the most common technique, which is used in computers on x86 platforms that increases the efficiency of virtual machine to handle various tasks • The working of virtualization technique wants catching the execution of privileged instructions by virtual machine, which passes these instructions to VMM to be handled properly.
- 9. • This is necessary because of the possible existence of multiple virtual machines, each having its own OS that could issue separate privileged instructions. Execution of privileged instructions needed complete attention of CPU. If, this is not managed properly by VMM, and it will raise an exception, which will result in system crash. • Trapping and forwarding the instructions to VMM, helps in managing the system suitably, and thereby avoiding different risks.
- 10. Virtualization at OS (operating system) level • To overcome redundancy and time consumption issues, virtualization at the operating system level is implemented. This kind of technique includes the sharing of both the OS and hardware. The physical machine is being separated from logical structure (virtual system) by separate virtualization layer, which could be compared with VMMs in functions. This layer is built on the top of the OS, which could enable the user to access to multiple machines, which is isolated from others and is running independently.
- 11. Virtualization at library level • Programming the applications in more systems needs a widespread list of Application Program Interfaces (APIs) to be disseminated by implementing several libraries at user level. • These APIs are used to save users from miniature details involved with programming related to the OS and facilitate the programmers to write programs more easily. • At the user level library operation, a different virtual environment is provided, in that kind of perception. This virtual environment is created above the OS layer, which could expose a different class of binary interfaces together. • This type of virtualization is well-defined as an implementation of various set of ABIs (Application Binary Interfaces). The APIs are being implemented with the help of the base system and execute the function of ABI/API emulation.
- 12. Virtualization at application level • Application-level virtualization comes when you wish to virtualize only an application. It does not virtualize an entire platform or environment. • On an operating system, applications work as one process. Hence it is also known as process-level virtualization. • It is generally useful when running virtual machines with high-level languages. Here, the application sits on top of the virtualization layer, which is above the application program. • The application program is, in turn, residing in the operating system. • Programs written in high-level languages and compiled for an application-level virtual machine can run fluently here.
- 13. • The user level programs and the operating systems are executed on applications, which behave like real machines. The memory mapped I/O processing technique or I/O mapped input/output processing is used to deal with hardware .Thus, an application might be taken simply as a block of instructions, which are being executed on a machine. The Java Virtual Machine (JVM) carried a new aspect to virtualization and it is known as application level virtualization. • The main concept after this type of virtualization is to produce a virtual machine that works distinctly at the application level and functions in a way similar as a normal machine. We can run our applications on those virtual machines as if we are running our applications on physical machines.
- 15. Before virtualization, the operating system manages the hardware. After virtualization, a virtualization layer is inserted between the hardware and the OS. In such a case, the virtualization layer is responsible for converting portions of the real hardware into virtual hardware. Depending on the position of the virtualization layer, there are several classes of VM architectures, namely • Hypervisor architecture, • Paravirtualization • host-based virtualization. • The hypervisor is also known as the VMM (Virtual Machine Monitor). They both perform the same virtualization operations.
- 16. Hypervisor and Xen Architecture • Depending on the functionality, a hypervisor can assume a micro-kernel architecture like the Microsoft Hyper-V. Or it can assume a monolithic hypervisor architecture like the VMware ESX for server virtualization. • A micro-kernel hypervisor includes only the basic and unchanging functions (such as physical memory management and processor scheduling). The device drivers and other changeable components are outside the hypervisor. • A monolithic hypervisor implements all the aforementioned functions, including those of the device drivers. Therefore, the size of the hypervisor code of a micro-kernel hypervisor is smaller than that of a monolithic hypervisor.
- 17. Xen Architecture • Xen is an open source hypervisor program developed by Cambridge University. • Xen is a microkernel hypervisor, which separates the policy from the mechanism. It implements all the mechanisms, leaving the policy to be handled by Domain 0. Xen does not include any device drivers natively. It just provides a mechanism by which a guest OS can have direct access to the physical devices.
- 18. • Like other virtualization systems, many guest OSes can run on top of the hypervisor. The guest OS (privileged guest OS), which has control ability, is called Domain 0, and the others are called Domain U. It is first loaded when Xen boots without any file system drivers being available.Domain 0 is designed to access hardware directly and manage devices. • Therefore, one of the responsibilities of Domain 0 is to allocate and map hardware resources for the guest domains (the Domain U domains).
- 19. Binary Translation with Full Virtualization • Depending on implementation technologies, hardware virtualization can be classified into two categories: full virtualization and host-based virtualization. Full Virtualization • With full virtualization, noncritical instructions run on the hardware directly while critical instructions are discovered and replaced with traps into the VMM to be emulated by software. Both the hypervisor and VMM approaches are considered full virtualization. Noncritical instructions do not control hardware or threaten the security of the system, but critical instructions do. Therefore, running noncritical instructions on hardware not only can promote efficiency, but also can ensure system security.
- 22. Host-Based Virtualization • An alternative VM architecture is to install a virtualization layer on top of the host OS. This host OS is still responsible for managing the hardware. The guest OSes are installed and run on top of the virtualization layer. Dedicated applications may run on the VMs. Certainly, some other applications can also run with the host OS directly. This host based architecture has some distinct advantages, as enumerated next. First, the user can install this VM architecture without modifying the host OS. Second, the host-based approach appeals to many host machine configurations.
- 23. Para-Virtualization • It needs to modify the guest operating systems. A para-virtualized VM provides special APIs requiring substantial OS modifications in user applications. Performance degradation is a critical issue of a virtualized system. Figure illustrates the concept of a para-virtualized VM architecture. The guest OS are para-virtualized. They are assisted by an intelligent compiler to replace the non virtualizable OS instructions by hypercalls. The traditional x86 processor offers four instruction execution rings: Rings 0, 1, 2, and 3. The lower the ring number, the higher the privilege of instruction being executed. The OS is responsible for managing the hardware and the privileged instructions to execute at Ring 0, while user-level applications run at Ring 3
- 26. Types of Hypervisors • A hypervisor, also known as a virtual machine monitor or VMM. The hypervisor is a piece of software that allows us to build and run virtual machines which are abbreviated as VMs. • A hypervisor allows a single host computer to support multiple virtual machines (VMs) by sharing resources including memory and processing. • The hypervisor is a hardware virtualization technique that allows multiple guest operating systems (OS) to run on a single host system at the same time. Types of Hypervisor – There are two types of hypervisors: 1. Type 1 (Native Hypervisor or Bare metal hypervisor) 2. Type 2 (Hosted Hypervisor).
- 28. Type 1 (Native Hypervisor or Bare metal hypervisor) • The hypervisor runs directly on the underlying host system. It is also known as a “Native Hypervisor” or “Bare metal hypervisor”. It does not require any base server operating system. It has direct access to hardware resources. Examples of Type 1 hypervisors include VMware ESXi, Citrix XenServer, and Microsoft Hyper-V hypervisor. • They are usually faster and more powerful than hosted hypervisors. For these purposes, the majority of enterprise businesses opt for bare-metal hypervisors for their data center computing requirements.
- 29. Pros & Cons of Type-1 Hypervisor: • Pros: Such kinds of hypervisors are very efficient because they have direct access to the physical hardware resources(like Cpu, Memory, Network, and Physical storage). This causes the empowerment of the security because there is nothing any kind of the third party resource so that attacker couldn’t compromise with anything. • Cons: One problem with Type-1 hypervisors is that they usually need a dedicated separate machine to perform their operation and to instruct different VMs and control the host hardware resources.
- 30. TYPE-2 Hypervisor: • A Host operating system runs on the underlying host system. It is also known as ‘Hosted Hypervisor”. Such kind of hypervisors doesn’t run directly over the underlying hardware rather they run as an application in a Host system(physical machine). Basically, the software is installed on an operating system. Hypervisor asks the operating system to make hardware calls. An example of a Type 2 hypervisor includes VMware Player or Parallels Desktop. Hosted hypervisors are often found on endpoints like PCs.
- 31. Pros & Cons of Type-2 Hypervisor: • Pros: Such kind of hypervisors allows quick and easy access to a guest Operating System alongside the host machine running. These hypervisors usually come with additional useful features for guest machines. Such tools enhance the coordination between the host machine and the guest machine. • Cons: Here there is no direct access to the physical hardware resources so the efficiency of these hypervisors lags in performance as compared to the type-1 hypervisors, and potential security risks are also there an attacker can compromise the security weakness if there is access to the host operating system so he can also access the guest operating system.
- 32. Thank you