Sinsing Notebook Cloud Fifth: System virtualization

Virtualization is an abstract way of representing computer resources. Through virtualization, we can simplify the representation, access, and management of computer resources such as infrastructure, systems, and software, and provide a standard interface for these resources to accept input and provide output. There are many kinds of virtualization technologies, such as network virtualization, memory virtualization, Desktop virtualization and Application virtualization, and so on, we mainly introduce system virtualization.

System virtualization uses a hypervisor (virtual machine Monitor, referred to as VMM) to virtual and run one or more virtual machines (VMS) on a single physical machine, And these virtual machines can run a variety of software like real machines, and they are isolated from each other in terms of resource occupancy to ensure the security and stability of operations.

In the late 1950s, Christopher Strachey published a paper entitled "Time Sharing in Large Fast computes", which is considered to be the origin of system virtualization. In the mid 1960s, IBM introduced the world's first computer IBM7044 to support the virtual technology of the system. Recently, the system virtualization technology has been greatly welcomed and affirmed by the industry, and has become a very mainstream technology.

In running mode, there are two main types of hypervisor for system virtualization.  One is the hypervisor type, which runs directly on the hardware, is installed on the hardware in the form of a similar operating system, it provides performance close to the physical machine, and does a lot of optimizations on Io, mainly for server class applications, also known as Type1. where VMware Both Esx and Xen belong to this type. The second is a managed type, it is installed on the traditional operating system, although its performance is not as good as hypervisor (mainly because it and the hardware is separated by a layer of operating system), but its use and installation is very convenient, features are very rich, such as support three-dimensional acceleration and so on, often used in desktop applications, Also known as Type2. This type of representative has VMware Workstation and VirtualBox, and so on.

Classification of System Virtualization technologies:

(1) Hardware emulation. That is, emulation, which is managed mode, which creates a new simulated hardware program (Hardware VM) on the physical machine's operating system to emulate the desired hardware, and runs the virtual machine on the program, and the guest OS (guest OS) inside the virtual machine does not have to be modified. Well-known products include Bochs, QEMU and Microsoft's Vritual PC. Due to the ability to emulate hardware, hardware emulation is well suited to the development of operating systems and facilitates collaborative development of firmware and hardware. Firmware developers can use target hardware-based virtual machines to validate their actual code in a simulation environment without having to wait until the hardware is physically available to begin testing. Because it is a simulated hardware, it is relatively low in performance.

(2) Full virtualization, which is fully virtualization, is mainly to capture and handle virtualization-sensitive special instructions between the customer's operating system and hardware, so that the customer's operating system can run without modification, and the speed will vary according to the different implementations. But it can meet the needs of the user roughly. This approach is the most mature and common in the industry, and is a product of both managed and hypervisor models, with well-known products such as IBM Cp/cms,virtualbox, KVM, VMware Workstation, and VMware ESX. In full virtual mode, the customer operating system does not need to be modified, and the speed is also easy to use.

(3) Semi-virtualization, which is paravirtualization, has some similarities with full virtualization. It also leverages the hypervisor to share access to the underlying hardware, but because the guest operating system running on the hypervisor has integrated the code related to para-virtualization, this allows the guest operating system to work well with hypervisors for virtualization. We do not need to recompile or capture privileged instructions, which are very similar in performance to physical machines. The most classic product is Xen, and of course Microsoft's Hyper-V. Its architecture is more streamlined than full virtualization and has a certain advantage over overall speed, but it needs to be modified for the customer's operating system, so it's a hassle in terms of user experience.

(4) Hardware-assisted virtualization (Hardware assisted virtualization) is a hardware vendor, such as Intel/AMD, that improves performance by using software technology that is used by some full virtualization and para-virtualization. Because hardware-assisted virtualization enables the extraction of a large amount of complex virtualization logic from the software, it greatly simplifies the architecture of virtualized products. In terms of usage, hardware virtualization is often used to optimize full virtualization and semi-virtualization, rather than the original faction. The classic example is that VMware Workstation introduced hardware virtualization technologies in version 6.0, such as Intel's Vt-x and AMD Amd-v, which we can choose whether to turn on hardware-assisted virtualization when we use it. Hardware-assisted virtualization is now supported in mainstream full virtualization and para-virtualization in the market, and the industry typically uses HVM (Hardware virtual machine) to refer to hardware-assisted virtualization.

(5) Operating system level virtualization, which is the operating system levels virtualization, is virtualized by simple isolation of the server operating system, primarily for services such as VPS. This technique only makes minor modifications to the operating system, is inexpensive and performs well, but performs poorly at the resource isolation level and qualifies the model and version of the customer's operating system, which can be used for VPS services.

The use of System virtualization:

(1) Software testing. Configuring your test environment by using VirtualBox and VMware Workstation is not only much faster than physical, but it also eliminates the need to purchase too much expensive hardware. And their own snapshot capabilities also make it easy to save the state of the error, which can be useful for the communication between testers and programmers.

(2) Desktop applications. For example, desktop virtualization software, such as VirtualBox and VMware Workstation, allows users to use proprietary software from other platforms, such as Linux users who can access online banking based on Microsoft's ActiveX technology through a virtual Windows environment. And organizations can deploy sophisticated virtual desktop solutions that not only unify the management of their staff's desktop environment for increased security, but also reduce the acquisition and energy costs of desktop systems.

(3) Server integration. With VMware ESX and Xen, you can consolidate the workload on multiple physical machines onto a single physical machine, reducing expenses such as hardware, software, energy, and sites, and increasing server usage, greatly simplifying the complexity of your IT architecture.

(4) Automation management. Using DRS (Distributed Resource scheduing, distributed resource scheduling), live migration (dynamic Migration), DPM (Distributed Power Management, distributed power Management), and HA (Hig H availability, high availability) and other advanced virtualization management technology, can greatly improve the automation of data center management Chengdu, and achieve disaster tolerance.

(5) Accelerate application deployment. The introduction of the Virtualization Application publishing format OVF (open virtualization format, opening virtualization formats) not only makes it easier for third-party application vendors to publish applications, but also enables system administrators to deploy the application very simply. It is also easy to migrate between multiple data centers.

Sinsing Notebook Cloud Fifth: System virtualization