Virtualization and Cloud computing

Why is there a virtualization technology?

Each host has an operating system, which has a strong coupling of software and hardware, and a host often runs many applications, especially in a distributed, clustered environment. Application conflicts often occur, which also leads to low system resource utilization and high hardware costs. Not flexible enough.

Virtualization technology

Virtualize a computer into multiple logical computers. Colleagues run multiple logical computers on one computer. Each logical computer can run a different operating system, and applications can run in independent spaces without affecting each other. , Thereby significantly improving the working efficiency of the computer.

Advantage
Break the dependency of operating system and hardware
Management of operating systems and applications as a single entity through technology encapsulated into virtual machines
Strong security and fault isolation

Virtual machine is independent of hardware and can run on any hardware

Technical classification
Full virtualization technology: also known as hardware-assisted virtualization technology. The virtualization technology originally used was full virtualization technology. A software layer (hypervisor) was added between the virtual machine and the hardware, or the virtual machine monitor (VMM). ).
Hypervisor runs directly on physical hardware – KVM
Hypervisor runs on another operating system – QEMU and WINE

Paravirtualization technology: also known as paravirtualization technology, which is based on full virtualization, the guest operating system has been modified, a special API has been added, this API can optimize the instructions issued by the guest operating system, That is, the hypervisor does not need to consume certain resources for translation operations, so the workload of the hypervisor becomes very small, so the overall performance has also been greatly improved, but special APIs are required, so it is rarely used in practice.

Architecture classification
Habitat architecture: installing and running virtualization programs on top of the operating system depends on the host operating system's support for the device and the management of physical resources; the advantage is simple and easy to implement; the disadvantage is that the installation and running applications depend on the host operating system to the device Support; such as GXS Server, VMware Server, Workstation;

Bare metal architecture: install virtualization software directly on the hardware, install operating systems and applications on it, rely on the virtualization layer kernel and server console for management; the advantage is that the virtual machine already depends on the operating system and can support multiple operating systems, A variety of applications, more flexible; the disadvantage is that the development of the virtual layer kernel is difficult; for example, VMWare ESXI Server;

Why do you need cloud computing?
The US Environmental Protection Agency (EPA) researched the energy efficiency of services and data centers and found that, in fact, the server was only working 5% of the time, and the server was dormant at other times, which caused a lot of waste of computing resources.
For large enterprises, the duration of the peak traffic band is too short, and most of the time server resources are idle.

For small businesses, server hardware costs are high, additional hardware is attached, hardware depreciates quickly, and utilization and investment are not proportional.

Cloud Computing

The National Institute of Standards and Technology (NIST) defines that cloud computing is a pay-per-use model that provides usable, convenient, on-demand network access and access to a configurable computing resource sharing pool (network , Servers, storage, application software, services, etc.), these resources can be provided quickly, requiring little management work or little interaction with the service provider.

Technological change
Single host and multiple users: resource dependence, mutual influence, no isolation

Multiple virtual machines on the host: resource sharing and isolation

Classification
Private cloud: inside the enterprise;
Public cloud: service platform;
Hybrid cloud: The typical application scenarios are from heavy traffic to public cloud, and heavy traffic to private cloud;
Cloud platform selection criteria
The extensiveness of the API interface;
What kind of open source protocol to use for writing;

The maturity of the platform;

Cloud platform classification

reference link: https://www.alibabacloud.com/product

Perspective
        The use of computing resources and network resources is free and paid on demand, just like tap water.