Introduction to Xen, OpenVZ, KVM, Hyper-V, VMWare virtualization technologies

I. Xen

Developed by the University of Cambridge, Xen is fully partitioned based on hardware and can only allocate as many resources as are physically available, making it difficult to oversell. It can be divided into Xen-PV (paravirtualization), and Xen-HVM (full virtualization).

Memory and hard disk space cannot be oversold by Xen. When the parent server has only 16G memory and 100G hard disk, the Xen architecture (any virtualization) will directly occupy 1G memory and 25G hard disk of the server, so the performance of Xen is better than OpenVZ in the case of overselling.

Xen-PV: it is only applicable to Linux series VPS, but it has a lower performance loss, about 4% to 8% when compared to the parent machine.

Xen-HVM: You can install Windows or freely mount ISO files to install any system, but because it is fully virtualized, the performance loss is greater, ranging from 8% to 20% compared to the parent machine.

Applicable people: Customers who have a more adequate budget and want a higher performance of VPS

Available systems: Xen-PV: pure Linux, Xen-HVM: supports Windows, Linux, etc.

II. OpenVZ

OpenVZ (OVZ) is an OS-level server virtualization architecture based on the Linux platform that uses the kernel of SWsoft's Virutozzo virtualized server software product. This architecture directly calls the kernel in the parent server (mother machine) to simulate the generation of child servers (VPS, small machine), so it is virtualized with a performance loss of about 1-3 percent when compared to the parent server.

Of course, OpenVZ can oversell, which means that he can open a sub-server with a configuration of 1G RAM x 17+ units on a server with a total of 16G RAM. Because his virtual architecture relationship is based on how much the customer uses and how much is deducted from the parent server, the OpenVZ architecture VPS is less expensive. However, due to the overselling factor, if the service provider continues to oversell, the server's performance will suffer significantly.

Another feature of OpenVZ is that it makes a direct call to the kernel of the parent server, rendering some software unusable and some kernel files unmodifiable.

Applicable people: Newbie, low budget customers

Note: Resources are not unique to you, installation of VPN services requires attention to detect virtual network card support.

Available systems: Linux (Windows not supported)

III. KVM

Under Linux, KVM is a full-featured virtualization architecture. VPSs based on KVM architecture do not come with a system by default, but you can upload the ISO yourself or call the ISO that comes with the service provider to manually install the system. This is ideal for customers who enjoy building their own VPS.

Because the KVM architecture is a full-featured virtualization architecture with independent BIOS control, it has a greater impact on the performance of the parent server, so KVM-based VPS are more expensive, but KVM VPS are more free than other VPS architectures.

Note: Virtualization performance is slightly lower than Xen

Available systems: Windows, Linux series

IV. Hyper-V

Microsoft's Hyper-V virtualization product is used by the majority of domestic VPS providers, primarily due to its conversion to Windows customization, which is easier to manage. The current Hyper-V also supports Linux, though the performance hit is greater.

Hyper-V fully supports both 32-bit and 64-bit Windows systems. Windows is highly recommended if you are looking for a VPS with Hyper-V architecture.

Although Hyper-V cannot currently oversell memory, it can oversell hard drives, which are deducted based on customer usage. In general, servers do not run out of hard drives all of the time, so don't be concerned.

Applicable people: Windows system enthusiasts

Note: Linux operating system performance is lower

Available systems: Windows, Linux

V. VMWare

VMWare is a full-featured, fully virtualized software created by the world's leading provider of desktop-to-data center virtualization solutions. However, because VMWare is very expensive to license for a series of products like VPS (with standalone panels), most VMWare service providers will provide VPS through VMware Workstation.

VPS opened with VMware Workstation has no control panel; the operating system must be installed manually by the service provider; however, it is now very easy to find the God KEY for VMware Workstation online, saving VPS service providers a lot of money. Typically applied to new business VPS service providers.

Because the VMWare Workstation architecture is the same as the OpenVZ architecture, how much memory the child uses is deducted from the system, but it may cause the parent server to use Windows virtual memory if there is insufficient physical memory.

Applicable people: Customers who are serious about building a website

Note: No control panel

Available systems: Windows, Linux series

The above measure of overselling refers to memory and disk, other hardware conditions, such as network bandwidth and CPU, are not taken into account.

VI. The difference between Xen and OpenVZ

Xen consists of dom0 and domU. Dom0 is a virtualization of resources such as CPU, IO bus routes, etc. for different kernels working on DomU.

The advantage of this is that

1. there are fewer restrictions on the operating systems that can be run.
2. the crash of the system on domU will not affect other doms. Of course, there will still be problems when Dom0 fails.

Disadvantages:

1. the overhead will be larger because of the need for virtual CPU, BUS and other physical resources.

OpenVZ uses a completely different approach in that the virtual machines it creates all use the same kernel to work under.

The benefits of this are

1. good performance.

Disadvantages.

1. any kernel bug will endanger all virtual machines. The possibility of crashing due to kernel bugs is greatly increased. 2.
2. it requires a lot of changes to the kernel.

The most obvious distinction is that XEN VPS has swap zones, RHEL5-based OpenVZ VPS does not have swap zones, and RHEL6-based OpenVZ VPS has VSwap zones.

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