What is virtualization?

The definition of virtualization is "the process of abstracting the resources of a computer." In the abstract process, for different resources (such as storage devices, CPU, memory, network, etc.), and there are different virtualization categories, the more common are:

1, Resource virtualization: The main is to abstract some of the computer system resources. such as storage devices, networks, network names, and so on.

Disk partitioning and RAID are examples of storage device virtualization.

Virtual hosts are examples of Network name virtualization.

2, Application software virtualization: The main abstraction of the software, so that it does not need to rely on a specific operating environment, is what we often say green software (portable)

Common Application Virtualization tools include: SoftGRID, XenAPP, and VMware's ThinApp

Can be used for enterprise-class manufacturers mainly three: Vmware,citrix,ms
More mature products from three vendors are VMware esxi,xenserver,hyper-v, which are bare-metal virtualization
VMware ESXi focuses on server virtualization, technology is more mature, more features, support virtual machine system;
XenServer Focus on desktop virtualization, cost-effective, good network performance, suitable for rapid and large-scale deployment, support systems are also many, but do desktop can be released only MS system;
Hyper-V started at the latest, it seems to only support the MS Home system, belonging to the server-level

3, platform virtualization: mainly the main resources of the computer (CPU, memory, network card) abstraction, and access to these resources of the objects are accessed through the abstraction layer, that is, virtual machines.

(i) Causes of virtualization and classification of technology

A, the most common virtual machine software includes the following several important products:

VMware Workstation/server/esx Server;

Microsoft's virtual pc/server/hyper-v;

Citrix's Xen;

Sun's xVM, Qemu and so on.

b, the cause of enterprise adoption virtual machine

is because of the waste of hardware resources, the main problem is the low efficiency of hardware resources.

C, different virtual technology

In terms of software, virtual machine products are divided into several categories for different implementation technologies:

1) Full virtualization: This is the mainstream of the present. The main thing is that the client operating system does not need to make any modifications when it runs on this virtual product. such as VMware Workstation, VSphere, Microsoft's hypervisor, and so on.

2) Hardware-assisted virtualization (Hardware virtual machine HVM): When the operating system runs on it, it must rely on the hardware of the system to complete the process of virtualization. such as Intel's VT and ADM Adm-v also have VMware's Workstation6.5.1.

3) Partial virtualization: When the virtual machine is running, the system only provides partial virtualization and does not properly install the full operating system.

4) Semi-virtualized (Pan-virtualization): When the operating system is running on this product, the core must be modified to install successfully. Like the early Xen

5) Operating System level virtualization: This type of virtual machine can only emulate the host system. You can only run Linux systems on Windows,linux, such as on Windows.

6) Living Environment: the most common is the Linux user mode, under a Linux, in the application of software to run other Linux. There is a difference between this and the full virtualization of the alien architecture.

D, virtual machine product running layer.

Regardless of the architecture, all virtual machines have to abstract the hardware resources of the computer, there must be an arbitration mechanism to manage the resources after abstraction. This arbitration mechanism is generally referred to as hypervisor or virtual machine Monitor (VMM).

*hypervisor*:

Hypervisor is an intermediate software layer running between a physical server and an operating system that allows multiple operating systems and applications to share a set of underlying physical hardware, and therefore can also be seen as a "meta" operating system in a virtual environment that coordinates access to all physical devices and virtual machines on the server. Also called the Virtual machine Monitor. Hypervisor is at the heart of all virtualization technologies. The ability to support multi-workload migrations non-disruptively is the basic function of hypervisor. When the server starts and executes hypervisor, it allocates the appropriate amount of memory, CPU, network, and disk to each virtual machine and loads the guest operating system for all virtual machines.

Native schema (Bare-metal):

When the virtual machine is installed, it inserts a layer of hyperviso over the hardware of the system and then installs the operating system. There is little direct correlation between the operating system and the hardware.

On the native schema, hypervisor is installed directly on the hardware and takes over all the hardware resources. Because the hypervisor layer is very small (up to 32MB footprint) and does not manage too complex matters, it is only responsible for communication and resource coordination with the upper-level VM operating system, and the probability of a blue screen is smaller. The blue screen of any operating system on it will not affect other clients, so it is more suitable for enterprise applications.

Under native architecture, hypervisor directly with the computer's hardware (for example).

Of course, in order to maintain the stability and micro-kernel of the native-architecture virtual machine, it is not possible to put all the desktop product drivers, so the biggest problem is hardware compatibility. Most native architecture products support mainstream servers and storage devices, such as Nas, iSCSI, or FC Sans, and emphasize that these devices are officially tested to ensure stability in an enterprise operating environment. Most of the hardware used in a typical PC cannot run under a native schema virtual machine.

Mainstream products for native architectures:

VMware VSphere

Microsoft Hyper-V R2 (free)

Microsoft Windows R2 Hyper-V Role

Citrix Xenserver/xendesktop

Xen (Linux, open source)

QEMM (Linux, open source)

In order to guarantee stability, the native architecture must be hardware compatible with the hardware in the Compatibility table (HCL) to run.

Before you begin installing configuration ESXi, it is recommended that you check the VMware official Vsan compatibility guide
License the hardware configuration. The Vsan Compatibility Guide can be found on the following Web site:

Http://vmwa.re/vsanhcl

http://readynas.netgear.cn/Hardware_Compatibility_List/

Vsan has stringent requirements for disk, flash memory devices, and disk controllers.

Because of the multitude of choices, configuring a perfect Vsan host can be a complex thing.

Before discussing these components individually, you should know that there is another option: VSAN ready Nodes.

* Alien Architecture * (Hosted):

In the alien architecture, hypervisor is present on the operating system. The alien architecture is that hypervisor is seen as an application or service that runs on an already installed operating system.

The biggest feature of this type of product is that it must be done on an already installed operating system called the Alien Architecture (Hosted). The advantage of doing this is hardware compatibility. As long as the guest operating system can use the hardware, the virtual machine in the operating system can be used. However, this hypervisor, which runs on the desktop operating system, is considered as an application software on the operating system, although many hypervisor parts are placed in the kernel during installation, but the operating system in the VM will be unusable when there are any problems with the alien operating system. Can not meet the emphasis on security and stability of enterprise applications.

For example, the most famous virtual product, VMware Workstation or Microsoft Virtual Pc/server, must be installed on an operating system, such as Windows 7 or Windows Server 2003. If the operating system has a blue screen, the VM client on which it operates is, of course, completely blue. This is the alien architecture.

Mainstream products of the alien architecture

VMware Workstation (with Windows and Linux versions)

VMware Server (with Windows and Linux versions, free)

VMware Player (with Windows and Linux versions, free)

Microsoft Virtual PC 2007

Microsoft Virtual Server 2005 SP2 (free)

Microsoft Windows Virtual PC (only run on Windows 7, free)

Parallels Workstation

UN Virtual Box (acquired by Oracle)

E, hardware-supported virtualization

Most X86 vendors now have CPUs that support virtual machine directives, such as Intel's VT and AMD

The amd-v. How does the technology on these hardware help virtual machines?

1) In the absence of a virtual machine, when the operating system is running on hardware, the core usually runs at the RING0 level, running the application at the Ring3 level.

2) on the virtual machine of the native architecture, Hypervisor operates in RING0, and the operating system is downgraded to Ring1.

3) using hardware-supported virtualization, hypervisor to Ring1 and the OS back to RING0

The virtualization benefits of hardware support are:

1) speed up the operation of the client operating system and solve the compatibility problem.

2) in the virtual machine environment test, you can make nested (Nested) virtual environment.

(ii) Enterprise environment-focused virtual machines

After the hardware is selected correctly, the Enterprise virtual machine architecture to consider factors such as security, stability, high operational efficiency, high availability, cost and management.

1) The principle of service isolation (isolation).

Only one service is installed on an operating system.

2) Improve the efficiency of hardware resources.

Run multiple operating systems on a single entity server. This allows each system service to run on a single operating system, while multiple operating systems can run concurrently on the same entity server.

Not only maintain the service isolation, but also improve the efficiency of hardware resources. This is: Server consolidation (Consolidation).

3) High availability.

You can solve complex problems such as high availability, fault tolerance, load balancing, and backup.

Can solve the problem that the device cannot solve at present. such as Dynamic host migrations, fast data deduplication, unified desktop management, enterprise integration environments (never downtime).

In a VDI environment, a desktop operating system is a virtual file that can be deployed quickly.

4) Enterprise Desktop environment Management (multi-person)

is to move the client's desktop operating system all to the server's virtual machine. Each desktop user is connected to their own virtual machine (using RDP or special online software, such as Citrix's ICA).

The advantage is that in addition to saving a large amount of upgrades to the hardware budget, it is possible to centrally manage all desktop operating systems, whether it is patching, installing applications, managing user rights, etc. are very convenient.

VMware's Enterprise desktop management products are: VMware View

Citrix's Enterprise Desktop management products are: XenDesktop and XenServer5

Native Benchmark Products:

VMware V13/vsphere

Various special functions:

The biggest feature is the magic of virtual machine transfer after multiple ESX joins.

Vmotion is the most important feature in V13, and you can choose the resources that are most needed to run.

HA allows the virtual machine to restart on another computer as soon as the physical machine freezes.

What is virtualization?